Merge branch 'master' into run-tests

lib/postprocessing.py

@@ -1,4 +1,4 @@
-import re
+import search
 import fmt.comments
 
 def postprocess(answer, keyword, options, request_options=None):
@@ -49,42 +49,8 @@ def _filter_by_keyword(answer, keyword, options):
         answer.append(paragraph)
         return answer
 
-    def _paragraph_contains(paragraph, keyword, insensitive=False, word_boundaries=True):
-        """
-        Check if `paragraph` contains `keyword`.
-        Several keywords can be joined together using ~
-        For example: ~ssh~passphrase
-        """
-        answer = True
-
-        if '~' in keyword:
-            keywords = keyword.split('~')
-        else:
-            keywords = [keyword]
-
-        for kwrd in keywords:
-            regex = re.escape(kwrd)
-            if not word_boundaries:
-                regex = r"\b%s\b" % kwrd
-
-            if insensitive:
-                answer = answer and bool(re.search(regex, paragraph, re.IGNORECASE))
-            else:
-                answer = answer and bool(re.search(regex, paragraph))
-
-        return answer
-
-
-    if not keyword:
-        return answer
-
-    search_options = {
-        'insensitive': 'i' in options,
-        'word_boundaries': 'b' in options
-    }
-
     paragraphs = [p for p in _split_paragraphs(answer)
-                  if _paragraph_contains(p, keyword, **search_options)]
+                  if search.match(p, keyword, options=options)]
     if not paragraphs:
         return ""
 

lib/search.py

@@ -19,6 +19,8 @@ Configuration parameters:
     search.limit
 """
 
+import re
+
 from config import CONFIG
 from routing import get_answer_dict, get_topics_list
 
@@ -30,13 +32,60 @@ def _limited_entry():
         'format': "code",
     }
 
+def _parse_options(options):
+    """Parse search options string into optiond_dict
+    """
+
+    if options is None:
+        return {}
+
+    search_options = {
+        'insensitive': 'i' in options,
+        'word_boundaries': 'b' in options,
+        'recursive': 'r' in options,
+    }
+    return search_options
+
+def match(paragraph, keyword, options=None, options_dict=None):
+    """Search for each keyword from `keywords` in `page`
+    and if all of them are found, return `True`.
+    Otherwise return `False`.
+
+    Several keywords can be joined together using ~
+    For example: ~ssh~passphrase
+    """
+
+    if '~' in keyword:
+        keywords = keyword.split('~')
+    else:
+        keywords = [keyword]
+
+    if options_dict is None:
+        options_dict = _parse_options(options)
+
+    for kwrd in keywords:
+        if not kwrd:
+            continue
+
+        regex = re.escape(kwrd)
+        if options_dict["word_boundaries"]:
+            regex = r"\b%s\b" % kwrd
+
+        if options_dict["insensitive"]:
+            if not re.search(regex, paragraph, re.IGNORECASE):
+                return False
+        else:
+            if not re.search(regex, paragraph):
+                return False
+    return True
+
 def find_answers_by_keyword(directory, keyword, options="", request_options=None):
     """
     Search in the whole tree of all cheatsheets or in its subtree `directory`
     by `keyword`
     """
 
-    recursive = 'r' in options
+    options_dict = _parse_options(options)
 
     answers_found = []
     for topic in get_topics_list(skip_internal=True, skip_dirs=True):
@@ -45,13 +94,13 @@ def find_answers_by_keyword(directory, keyword, options="", request_options=None
             continue
 
         subtopic = topic[len(directory):]
-        if not recursive and '/' in subtopic:
+        if not options_dict["recursive"] and '/' in subtopic:
             continue
 
-        answer = get_answer_dict(topic, request_options=request_options)
-
-        if answer and answer.get('answer') and keyword.lower() in answer.get('answer', '').lower():
-            answers_found.append(answer)
+        answer_dict = get_answer_dict(topic, request_options=request_options)
+        answer_text = answer_dict.get('answer', '')
+        if match(answer_text, keyword, options_dict=options_dict):
+            answers_found.append(answer_dict)
 
         if len(answers_found) > CONFIG['search.limit']:
             answers_found.append(

share/cht.sh.txt

@@ -24,8 +24,8 @@
 # count words in text counter
 # group elements list
 
-__CHTSH_VERSION=6
-__CHTSH_DATETIME="2019-06-05 18:00:46 +0200"
+__CHTSH_VERSION=0.0.1
+__CHTSH_DATETIME="2020-08-05 09:30:30 +0200"
 
 # cht.sh configuration loading
 #
@@ -80,6 +80,8 @@ cheatsh_standalone_install()
   local installdir; installdir="$1"
   local default_installdir="$HOME/.cheat.sh"
 
+  [ -z "$installdir" ] && installdir=${default_installdir}
+
   if [ "$installdir" = help ]; then
     cat <<EOF
 Install cheat.sh in the standalone mode.
@@ -128,8 +130,9 @@ EOF
   [ "$_exit_code" -ne 0 ] && return "$_exit_code"
 
   while true; do
-    echo -n "Where should cheat.sh be installed [$default_installdir]? "; read -r installdir
-    [ -n "$installdir" ] || installdir="$default_installdir"
+    local _installdir
+    echo -n "Where should cheat.sh be installed [$installdir]? "; read -r _installdir
+    [ -n "$_installdir" ] && installdir=$_installdir
 
     if [ "$installdir" = y ] \
         || [ "$installdir" = Y ] \
@@ -172,8 +175,8 @@ EOF
 
   # after the repository cloned, we may have the log directory
   # and we can write our installation log into it
-  mkdir -p "$installdir/log/"
-  LOG="$installdir/log/install.log"
+  mkdir -p "log/"
+  LOG="$PWD/log/install.log"
 
   # we use tee everywhere so we should set -o pipefail
   set -o pipefail
@@ -184,7 +187,7 @@ EOF
   # set PYTHON2 to NO:
   # PYTHON2=NO
   #
-  PYTHON2=YES
+  PYTHON2=NO
   if [[ $PYTHON2 = YES ]]; then
     python="python2"
     pip="pip"
@@ -199,6 +202,8 @@ EOF
   "$python" "$(command -v virtualenv)" "${virtualenv_python3_option[@]}" ve \
       || fatal Could not create virtual environment with "python2 $(command -v virtualenv) ve"
 
+  export CHEATSH_PATH_WORKDIR=$PWD
+
   # rapidfuzz does not support Python 2,
   # so if we are using Python 2, install fuzzywuzzy instead
   if [[ $PYTHON2 = YES ]]; then

tests/results/1

@@ -1,10 +1,12 @@
+1_Inheritance
 1line
+2_Multiple_Inheritance
 :learn
 :list
 Advanced
 Classes
 Comments
-Control_Flow
+Control_Flow_and_Iterables
 Functions
 Modules
 Primitive_Datatypes_and_Operators
@@ -13,6 +15,7 @@ doc
 func
 hello
 lambda
+list_comprehension
 loops
 recursion
 rosetta/

tests/results/16

@@ -2,15 +2,15 @@
 
 1ns                          Main memory reference:       Send 2,000 bytes             Read 1,000,000 bytes         
 ▗▖                           100ns                        over commodity network:      sequentially from SSD:       
-                             ▗▖                           62ns                         61.712us                     
+                             ▗▖                           44ns                         48.981us                     
 L1 cache reference: 1ns                                   ▗                            ▗                            
 ▗▖                           1.0us                                                                                  
-                             ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         SSD random read: 16.0us      Disk seek: 2.679433ms        
-Branch mispredict: 3ns                                    ▗▖▗                          ▗▖▗▖▗                        
+                             ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         SSD random read: 16.0us      Disk seek: 2.499999ms        
+Branch mispredict: 3ns                                    ▗▖▗                          ▗▖▗▖                         
 ▗▖▗▖▗▖                                                                                                              
-                             Compress 1KB with Snappy:     Read 1,000,000 bytes         Read 1,000,000 bytes         
+                             Compress 1KB wth Snappy:     Read 1,000,000 bytes         Read 1,000,000 bytes         
 L2 cache reference: 4ns      2.0us                        sequentially from memory:    sequentially from disk:      
-▗▖▗▖▗▖▗▖                     ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         3.738us                      947.322us                    
+▗▖▗▖▗▖▗▖                     ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         2.967us                      824.692us                    
                              ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         ▗                            ▗                            
 Mutex lock/unlock: 16ns                                                                                             
 ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖                                      Round trip                   Packet roundtrip             

tests/results/17

@@ -1,33 +1,33 @@
-# Microsoft Azure CLI 2.0
-# Command-line tools for Azure
+# Microsoft Azure CLI 2.0
+# Command-line tools for Azure
 
-# Install Azure CLI 2.0 with one curl command.
+# Install Azure CLI 2.0 with one curl command.
 curl -L https://aka.ms/InstallAzureCli | bash
 
-# create a resource group named "MyResourceGroup" in the westus2 region of Azure
-az group create -n MyResourceGroup -l westus2 
+# create a resource group named "MyResourceGroup" in the westus2 region of Azure
+az group create -n MyResourceGroup -l westus2
 
-# create a Linux VM using the UbuntuTLS image, with two attached storage disks of 10 GB and 20 GB
+# create a Linux VM using the UbuntuTLS image, with two attached storage disks of 10 GB and 20 GB
 az vm create -n MyLinuxVM -g MyResourceGroup --ssh-key-value $HOME/.ssh/id_rsa.pub --image UbuntuLTS --data-disk-sizes-gb 10 20
 
-# list VMs
+# list VMs
 az vm list --output table
 
-# list only VMs having distinct state
+# list only VMs having distinct state
 az vm list -d --query "[?powerState=='VM running']" --output table
 
-# delete VM (with the name MyLinuxVM in the group MyResourceGroup)
+# delete VM (with the name MyLinuxVM in the group MyResourceGroup)
 az vm delete -g MyResourceGroup -n MyLinuxVM --yes
 
-# Delete all VMs in a resource group
+# Delete all VMs in a resource group
 az vm delete --ids $(az vm list -g MyResourceGroup --query "[].id" -o tsv)
 
-# Create an Image based on a running VM
+# Create an Image based on a running VM
 az vm deallocate -g MyResourceGroup -n MyLinuxVM
 az vm generalize -g MyResourceGroup -n MyLinuxVM
 az image create --resource-group MyResourceGroup --name MyTestImage --source MyLinuxVM
 
-# Running VM based on a VHD
+# Running VM based on a VHD
 az storage blob upload --account-name "${account_name}"  \
    --account-key "${account_key}" --container-name "${container_name}" --type page \
    --file "${file}" --name "${vhd_name}"
@@ -36,55 +36,55 @@
    --name myManagedDisk \
    --source https://${account_name}.blob.core.windows.net/${container_name}/${vhd_name}
 
-# open port
+# open port
 az vm open-port --resource-group MyResourceGroup --name MyLinuxVM --port 443 --priority 899
 
-# Show storage accounts
+# Show storage accounts
 az storage account list --output table
 
-# Show contaniers for an account
+# Show contaniers for an account
 az storage container list --account-name mystorageaccount --output table
 
-# Show blobs in a container
+# Show blobs in a container
 az storage blob list --account-name mystorageaccount --container-name mycontainer  --output table
 
-# list account keys
+# list account keys
 az storage account keys list  --account-name STORAGE_NAME --resource-group RESOURCE_GROUP
 
-# Show own images
+# Show own images
 az image list --output table
 
-# Configure default storage location
+# Configure default storage location
 az configure --defaults location=eastus2
 
-# Show disks
+# Show disks
 az disk list --output table
 
-# Copy blob
+# Copy blob
 az storage blob copy start \
-	--source-uri 'https://md-ldh5nknx2rkz.blob.core.windows.net/jzwuuuzzapn0/abcd?sv=2017-04-17&sr=b&si=68041718-6828-4f5e-9e6e-a1b719975062&sig=XXX' \
-	--account-key XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== \
-	--account-name destaccount \
-	--destination-container vms \
-	--destination-blob DESTINATION-blob.vhd
+    --source-uri 'https://md-ldh5nknx2rkz.blob.core.windows.net/jzwuuuzzapn0/abcd?sv=2017-04-17&sr=b&si=68041718-6828-4f5e-9e6e-a1b719975062&sig=XXX' \
+    --account-key XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== \
+    --account-name destaccount \
+    --destination-container vms \
+    --destination-blob DESTINATION-blob.vhd
 
-# List virtual networks
+# List virtual networks
 az network vnet list --output table
 
-# List virtual networks adapters
+# List virtual networks adapters
 az network nic list --output table
 
-# List public IP addresses used by the VMs
+# List public IP addresses used by the VMs
 az vm list-ip-addresses --output table
 
-# create snapshot
+# create snapshot
 az snapshot create --resource-group IC-EXASOL-001 --source vm1-disk1 -n vm1-snap1
 
-# create SAS url for a snapshot
+# create SAS url for a snapshot
 az snapshot grant-access --resource-group IC-EXASOL-001 --name vm1-snap1 --duration-in-seconds 36000 --query '[accessSas]' -o tsv
 
-# attach disk
+# attach disk
 az vm disk attach --vm-name vm1 -g RESOURCE_GROUP --disk DISK1_ID
 
-# detach disk
+# detach disk
 az vm disk detach --vm-name vm1 -g RESOURCE_GROUP --name DISK1_ID

tests/results/18

@@ -1,19 +1,19 @@
 >>> s = 'abcdefgh'
 >>> n, m, char, chars = 2, 3, 'd', 'cd'
->>> # starting from n=2 characters in and m=3 in length;
+>>> # starting from n=2 characters in and m=3 in length;
 >>> s[n-1:n+m-1]
 'bcd'
->>> # starting from n characters in, up to the end of the string;
+>>> # starting from n characters in, up to the end of the string;
 >>> s[n-1:]
 'bcdefgh'
->>> # whole string minus last character;
+>>> # whole string minus last character;
 >>> s[:-1]
 'abcdefg'
->>> # starting from a known character char="d" within the string and of m length;
+>>> # starting from a known character char="d" within the string and of m length;
 >>> indx = s.index(char)
 >>> s[indx:indx+m]
 'def'
->>> # starting from a known substring chars="cd" within the string and of m length.
+>>> # starting from a known substring chars="cd" within the string and of m length.
 >>> indx = s.index(chars)
 >>> s[indx:indx+m]
 'cde'

tests/results/2

@@ -1,17 +1,17 @@
-# Displays everything in the target directory
-ls path/to/the/target/directory
+# To display everything in <dir>, excluding hidden files:
+ls <dir>
 
-# Displays everything including hidden files
-ls -a
+# To display everything in <dir>, including hidden files:
+ls -a <dir>
 
-# Displays all files, along with the size (with unit suffixes) and timestamp
-ls -lh 
+# To display all files, along with the size (with unit suffixes) and timestamp
+ls -lh <dir>
 
-# Display files, sorted by size
-ls -S
+# To display files, sorted by size:
+ls -S <dir>
 
-# Display directories only
-ls -d */
+# To display directories only:
+ls -d */ <dir>
 
-# Display directories only, include hidden
-ls -d .*/ */
+# To display directories only, include hidden:
+ls -d .*/ */ <dir>

tests/results/20

@@ -65,7 +65,9 @@ Bitmap-Bresenhams-line-algorithm
 Bitmap-Flood-fill
 Bitmap-Histogram
 Bitmap-Midpoint-circle-algorithm
+Bitmap-PPM-conversion-through-a-pipe
 Bitmap-Read-a-PPM-file
+Bitmap-Read-an-image-through-a-pipe
 Bitmap-Write-a-PPM-file
 Bitwise-IO
 Bitwise-operations
@@ -92,10 +94,12 @@ Casting-out-nines
 Catalan-numbers
 Catalan-numbers-Pascals-triangle
 Catamorphism
+Catmull-Clark-subdivision-surface
 Character-codes
 Chat-server
 Check-Machin-like-formulas
 Check-that-file-exists
+Checkpoint-synchronization
 Chinese-remainder-theorem
 Cholesky-decomposition
 Circles-of-given-radius-through-two-points
@@ -107,6 +111,7 @@ Color-of-a-screen-pixel
 Color-quantization
 Colour-bars-Display
 Colour-pinstripe-Display
+Colour-pinstripe-Printer
 Combinations
 Combinations-and-permutations
 Combinations-with-repetitions
@@ -141,6 +146,7 @@ Day-of-the-week
 Deal-cards-for-FreeCell
 Death-Star
 Deconvolution-1D
+Deconvolution-2D+
 Deepcopy
 Define-a-primitive-data-type
 Delegates
@@ -689,6 +695,7 @@ Variadic-function
 Vector-products
 Verify-distribution-uniformity-Chi-squared-test
 Verify-distribution-uniformity-Naive
+Video-display-modes
 Vigen-re-cipher
 Vigen-re-cipher-Cryptanalysis
 Visualize-a-tree
@@ -715,6 +722,7 @@ Y-combinator
 Yahoo--search-interface
 Yin-and-yang
 Zebra-puzzle
+Zeckendorf-arithmetic
 Zeckendorf-number-representation
 Zero-to-the-zero-power
 Zhang-Suen-thinning-algorithm

tests/results/21

@@ -1,270 +1,270 @@
-// Single-line comments start with two slashes.
-/* Multiline comments start with slash-star,
-   and end with star-slash */
+// Single-line comments start with two slashes.
+/* Multiline comments start with slash-star,
+   and end with star-slash */
 
-// Statements can be terminated by ;
+// Statements can be terminated by ;
 doStuff();
 
-// ... but they don't have to be, as semicolons are automatically inserted
-// wherever there's a newline, except in certain cases.
+// ... but they don't have to be, as semicolons are automatically inserted
+// wherever there's a newline, except in certain cases.
 doStuff()
 
-// Because those cases can cause unexpected results, we'll keep on using
-// semicolons in this guide.
+// Because those cases can cause unexpected results, we'll keep on using
+// semicolons in this guide.
 
-///////////////////////////////////
-// 1. Numbers, Strings and Operators
+///////////////////////////////////
+// 1. Numbers, Strings and Operators
 
-// JavaScript has one number type (which is a 64-bit IEEE 754 double).
-// Doubles have a 52-bit mantissa, which is enough to store integers
-// up to about 9✕10¹⁵ precisely.
-3; // = 3
-1.5; // = 1.5
+// JavaScript has one number type (which is a 64-bit IEEE 754 double).
+// Doubles have a 52-bit mantissa, which is enough to store integers
+// up to about 9✕10¹⁵ precisely.
+3; // = 3
+1.5; // = 1.5
 
-// Some basic arithmetic works as you'd expect.
-1 + 1; // = 2
-0.1 + 0.2; // = 0.30000000000000004
-8 - 1; // = 7
-10 * 2; // = 20
-35 / 5; // = 7
+// Some basic arithmetic works as you'd expect.
+1 + 1; // = 2
+0.1 + 0.2; // = 0.30000000000000004
+8 - 1; // = 7
+10 * 2; // = 20
+35 / 5; // = 7
 
-// Including uneven division.
-5 / 2; // = 2.5
+// Including uneven division.
+5 / 2; // = 2.5
 
-// And modulo division.
-10 % 2; // = 0
-30 % 4; // = 2
-18.5 % 7; // = 4.5
+// And modulo division.
+10 % 2; // = 0
+30 % 4; // = 2
+18.5 % 7; // = 4.5
 
-// Bitwise operations also work; when you perform a bitwise operation your float
-// is converted to a signed int *up to* 32 bits.
-1 << 2; // = 4
+// Bitwise operations also work; when you perform a bitwise operation your float
+// is converted to a signed int *up to* 32 bits.
+1 << 2; // = 4
 
-// Precedence is enforced with parentheses.
-(1 + 3) * 2; // = 8
+// Precedence is enforced with parentheses.
+(1 + 3) * 2; // = 8
 
-// There are three special not-a-real-number values:
-Infinity; // result of e.g. 1/0
--Infinity; // result of e.g. -1/0
-NaN; // result of e.g. 0/0, stands for 'Not a Number'
+// There are three special not-a-real-number values:
+Infinity; // result of e.g. 1/0
+-Infinity; // result of e.g. -1/0
+NaN; // result of e.g. 0/0, stands for 'Not a Number'
 
-// There's also a boolean type.
+// There's also a boolean type.
 true;
 false;
 
-// Strings are created with ' or ".
+// Strings are created with ' or ".
 'abc';
 "Hello, world";
 
-// Negation uses the ! symbol
-!true; // = false
-!false; // = true
+// Negation uses the ! symbol
+!true; // = false
+!false; // = true
 
-// Equality is ===
-1 === 1; // = true
-2 === 1; // = false
+// Equality is ===
+1 === 1; // = true
+2 === 1; // = false
 
-// Inequality is !==
-1 !== 1; // = false
-2 !== 1; // = true
+// Inequality is !==
+1 !== 1; // = false
+2 !== 1; // = true
 
-// More comparisons
-1 < 10; // = true
-1 > 10; // = false
-2 <= 2; // = true
-2 >= 2; // = true
+// More comparisons
+1 < 10; // = true
+1 > 10; // = false
+2 <= 2; // = true
+2 >= 2; // = true
 
-// Strings are concatenated with +
-"Hello " + "world!"; // = "Hello world!"
+// Strings are concatenated with +
+"Hello " + "world!"; // = "Hello world!"
 
-// ... which works with more than just strings
-"1, 2, " + 3; // = "1, 2, 3"
-"Hello " + ["world", "!"]; // = "Hello world,!"
+// ... which works with more than just strings
+"1, 2, " + 3; // = "1, 2, 3"
+"Hello " + ["world", "!"]; // = "Hello world,!"
 
-// and are compared with < and >
-"a" < "b"; // = true
+// and are compared with < and >
+"a" < "b"; // = true
 
-// Type coercion is performed for comparisons with double equals...
-"5" == 5; // = true
-null == undefined; // = true
+// Type coercion is performed for comparisons with double equals...
+"5" == 5; // = true
+null == undefined; // = true
 
-// ...unless you use ===
-"5" === 5; // = false
-null === undefined; // = false
+// ...unless you use ===
+"5" === 5; // = false
+null === undefined; // = false
 
-// ...which can result in some weird behaviour...
-13 + !0; // 14
-"13" + !0; // '13true'
+// ...which can result in some weird behaviour...
+13 + !0; // 14
+"13" + !0; // '13true'
 
-// You can access characters in a string with `charAt`
-"This is a string".charAt(0);  // = 'T'
+// You can access characters in a string with `charAt`
+"This is a string".charAt(0);  // = 'T'
 
-// ...or use `substring` to get larger pieces.
-"Hello world".substring(0, 5); // = "Hello"
+// ...or use `substring` to get larger pieces.
+"Hello world".substring(0, 5); // = "Hello"
 
-// `length` is a property, so don't use ().
-"Hello".length; // = 5
+// `length` is a property, so don't use ().
+"Hello".length; // = 5
 
-// There's also `null` and `undefined`.
-null;      // used to indicate a deliberate non-value
-undefined; // used to indicate a value is not currently present (although
-           // `undefined` is actually a value itself)
+// There's also `null` and `undefined`.
+null;      // used to indicate a deliberate non-value
+undefined; // used to indicate a value is not currently present (although
+           // `undefined` is actually a value itself)
 
-// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
-// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
+// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
+// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
 
-///////////////////////////////////
-// 2. Variables, Arrays and Objects
+///////////////////////////////////
+// 2. Variables, Arrays and Objects
 
-// Variables are declared with the `var` keyword. JavaScript is dynamically
-// typed, so you don't need to specify type. Assignment uses a single `=`
-// character.
+// Variables are declared with the `var` keyword. JavaScript is dynamically
+// typed, so you don't need to specify type. Assignment uses a single `=`
+// character.
 var someVar = 5;
 
-// If you leave the var keyword off, you won't get an error...
+// If you leave the var keyword off, you won't get an error...
 someOtherVar = 10;
 
-// ...but your variable will be created in the global scope, not in the scope
-// you defined it in.
+// ...but your variable will be created in the global scope, not in the scope
+// you defined it in.
 
-// Variables declared without being assigned to are set to undefined.
-var someThirdVar; // = undefined
+// Variables declared without being assigned to are set to undefined.
+var someThirdVar; // = undefined
 
-// If you want to declare a couple of variables, then you could use a comma
-// separator
+// If you want to declare a couple of variables, then you could use a comma
+// separator
 var someFourthVar = 2, someFifthVar = 4;
 
-// There's shorthand for performing math operations on variables:
-someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
-someVar *= 10; // now someVar is 100
+// There's shorthand for performing math operations on variables:
+someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
+someVar *= 10; // now someVar is 100
 
-// and an even-shorter-hand for adding or subtracting 1
-someVar++; // now someVar is 101
-someVar--; // back to 100
+// and an even-shorter-hand for adding or subtracting 1
+someVar++; // now someVar is 101
+someVar--; // back to 100
 
-// Arrays are ordered lists of values, of any type.
+// Arrays are ordered lists of values, of any type.
 var myArray = ["Hello", 45, true];
 
-// Their members can be accessed using the square-brackets subscript syntax.
-// Array indices start at zero.
-myArray[1]; // = 45
+// Their members can be accessed using the square-brackets subscript syntax.
+// Array indices start at zero.
+myArray[1]; // = 45
 
-// Arrays are mutable and of variable length.
+// Arrays are mutable and of variable length.
 myArray.push("World");
-myArray.length; // = 4
+myArray.length; // = 4
 
-// Add/Modify at specific index
+// Add/Modify at specific index
 myArray[3] = "Hello";
 
-// Add and remove element from front or back end of an array
-myArray.unshift(3); // Add as the first element
-someVar = myArray.shift(); // Remove first element and return it
-myArray.push(3); // Add as the last element
-someVar = myArray.pop(); // Remove last element and return it
+// Add and remove element from front or back end of an array
+myArray.unshift(3); // Add as the first element
+someVar = myArray.shift(); // Remove first element and return it
+myArray.push(3); // Add as the last element
+someVar = myArray.pop(); // Remove last element and return it
 
-// Join all elements of an array with semicolon
+// Join all elements of an array with semicolon
 var myArray0 = [32,false,"js",12,56,90];
-myArray0.join(";") // = "32;false;js;12;56;90"
+myArray0.join(";"); // = "32;false;js;12;56;90"
 
-// Get subarray of elements from index 1 (include) to 4 (exclude)
-myArray0.slice(1,4); // = [false,"js",12]
+// Get subarray of elements from index 1 (include) to 4 (exclude)
+myArray0.slice(1,4); // = [false,"js",12]
 
-// Remove 4 elements starting from index 2, and insert there strings
-// "hi","wr" and "ld"; return removed subarray
-myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
-// myArray0 === [32,false,"hi","wr","ld"]
+// Remove 4 elements starting from index 2, and insert there strings
+// "hi","wr" and "ld"; return removed subarray
+myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
+// myArray0 === [32,false,"hi","wr","ld"]
 
-// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
-// languages: an unordered collection of key-value pairs.
+// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
+// languages: an unordered collection of key-value pairs.
 var myObj = {key1: "Hello", key2: "World"};
 
-// Keys are strings, but quotes aren't required if they're a valid
-// JavaScript identifier. Values can be any type.
+// Keys are strings, but quotes aren't required if they're a valid
+// JavaScript identifier. Values can be any type.
 var myObj = {myKey: "myValue", "my other key": 4};
 
-// Object attributes can also be accessed using the subscript syntax,
-myObj["my other key"]; // = 4
+// Object attributes can also be accessed using the subscript syntax,
+myObj["my other key"]; // = 4
 
-// ... or using the dot syntax, provided the key is a valid identifier.
-myObj.myKey; // = "myValue"
+// ... or using the dot syntax, provided the key is a valid identifier.
+myObj.myKey; // = "myValue"
 
-// Objects are mutable; values can be changed and new keys added.
+// Objects are mutable; values can be changed and new keys added.
 myObj.myThirdKey = true;
 
-// If you try to access a value that's not yet set, you'll get undefined.
-myObj.myFourthKey; // = undefined
+// If you try to access a value that's not yet set, you'll get undefined.
+myObj.myFourthKey; // = undefined
 
-///////////////////////////////////
-// 3. Logic and Control Structures
+///////////////////////////////////
+// 3. Logic and Control Structures
 
-// The `if` structure works as you'd expect.
+// The `if` structure works as you'd expect.
 var count = 1;
 if (count == 3){
-    // evaluated if count is 3
+    // evaluated if count is 3
 } else if (count == 4){
-    // evaluated if count is 4
+    // evaluated if count is 4
 } else {
-    // evaluated if it's not either 3 or 4
+    // evaluated if it's not either 3 or 4
 }
 
-// As does `while`.
+// As does `while`.
 while (true){
-    // An infinite loop!
+    // An infinite loop!
 }
 
-// Do-while loops are like while loops, except they always run at least once.
+// Do-while loops are like while loops, except they always run at least once.
 var input;
 do {
     input = getInput();
 } while (!isValid(input));
 
-// The `for` loop is the same as C and Java:
-// initialization; continue condition; iteration.
+// The `for` loop is the same as C and Java:
+// initialization; continue condition; iteration.
 for (var i = 0; i < 5; i++){
-    // will run 5 times
+    // will run 5 times
 }
 
-// Breaking out of labeled loops is similar to Java
+// Breaking out of labeled loops is similar to Java
 outer:
 for (var i = 0; i < 10; i++) {
     for (var j = 0; j < 10; j++) {
         if (i == 5 && j ==5) {
             break outer;
-            // breaks out of outer loop instead of only the inner one
+            // breaks out of outer loop instead of only the inner one
         }
     }
 }
 
-// The for/in statement allows iteration over properties of an object.
+// The for/in statement allows iteration over properties of an object.
 var description = "";
 var person = {fname:"Paul", lname:"Ken", age:18};
 for (var x in person){
     description += person[x] + " ";
-} // description = 'Paul Ken 18 '
+} // description = 'Paul Ken 18 '
 
-// The for/of statement allows iteration over iterable objects (including the built-in String, 
-// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
-// and user-defined iterables).
+// The for/of statement allows iteration over iterable objects (including the built-in String, 
+// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
+// and user-defined iterables).
 var myPets = "";
 var pets = ["cat", "dog", "hamster", "hedgehog"];
 for (var pet of pets){
     myPets += pet + " ";
-} // myPets = 'cat dog hamster hedgehog '
+} // myPets = 'cat dog hamster hedgehog '
 
-// && is logical and, || is logical or
+// && is logical and, || is logical or
 if (house.size == "big" && house.colour == "blue"){
     house.contains = "bear";
 }
 if (colour == "red" || colour == "blue"){
-    // colour is either red or blue
+    // colour is either red or blue
 }
 
-// && and || "short circuit", which is useful for setting default values.
+// && and || "short circuit", which is useful for setting default values.
 var name = otherName || "default";
 
-// The `switch` statement checks for equality with `===`.
-// Use 'break' after each case
-// or the cases after the correct one will be executed too.
+// The `switch` statement checks for equality with `===`.
+// Use 'break' after each case
+// or the cases after the correct one will be executed too.
 grade = 'B';
 switch (grade) {
   case 'A':
@@ -282,172 +282,172 @@
 }
 
 
-///////////////////////////////////
-// 4. Functions, Scope and Closures
+///////////////////////////////////
+// 4. Functions, Scope and Closures
 
-// JavaScript functions are declared with the `function` keyword.
+// JavaScript functions are declared with the `function` keyword.
 function myFunction(thing){
     return thing.toUpperCase();
 }
-myFunction("foo"); // = "FOO"
+myFunction("foo"); // = "FOO"
 
-// Note that the value to be returned must start on the same line as the
-// `return` keyword, otherwise you'll always return `undefined` due to
-// automatic semicolon insertion. Watch out for this when using Allman style.
+// Note that the value to be returned must start on the same line as the
+// `return` keyword, otherwise you'll always return `undefined` due to
+// automatic semicolon insertion. Watch out for this when using Allman style.
 function myFunction(){
-    return // <- semicolon automatically inserted here
+    return // <- semicolon automatically inserted here
     {thisIsAn: 'object literal'};
 }
-myFunction(); // = undefined
+myFunction(); // = undefined
 
-// JavaScript functions are first class objects, so they can be reassigned to
-// different variable names and passed to other functions as arguments - for
-// example, when supplying an event handler:
+// JavaScript functions are first class objects, so they can be reassigned to
+// different variable names and passed to other functions as arguments - for
+// example, when supplying an event handler:
 function myFunction(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }
 setTimeout(myFunction, 5000);
-// Note: setTimeout isn't part of the JS language, but is provided by browsers
-// and Node.js.
+// Note: setTimeout isn't part of the JS language, but is provided by browsers
+// and Node.js.
 
-// Another function provided by browsers is setInterval
+// Another function provided by browsers is setInterval
 function myFunction(){
-    // this code will be called every 5 seconds
+    // this code will be called every 5 seconds
 }
 setInterval(myFunction, 5000);
 
-// Function objects don't even have to be declared with a name - you can write
-// an anonymous function definition directly into the arguments of another.
+// Function objects don't even have to be declared with a name - you can write
+// an anonymous function definition directly into the arguments of another.
 setTimeout(function(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }, 5000);
 
-// JavaScript has function scope; functions get their own scope but other blocks
-// do not.
+// JavaScript has function scope; functions get their own scope but other blocks
+// do not.
 if (true){
     var i = 5;
 }
-i; // = 5 - not undefined as you'd expect in a block-scoped language
+i; // = 5 - not undefined as you'd expect in a block-scoped language
 
-// This has led to a common pattern of "immediately-executing anonymous
-// functions", which prevent temporary variables from leaking into the global
-// scope.
+// This has led to a common pattern of "immediately-executing anonymous
+// functions", which prevent temporary variables from leaking into the global
+// scope.
 (function(){
     var temporary = 5;
-    // We can access the global scope by assigning to the "global object", which
-    // in a web browser is always `window`. The global object may have a
-    // different name in non-browser environments such as Node.js.
+    // We can access the global scope by assigning to the "global object", which
+    // in a web browser is always `window`. The global object may have a
+    // different name in non-browser environments such as Node.js.
     window.permanent = 10;
 })();
-temporary; // raises ReferenceError
-permanent; // = 10
+temporary; // raises ReferenceError
+permanent; // = 10
 
-// One of JavaScript's most powerful features is closures. If a function is
-// defined inside another function, the inner function has access to all the
-// outer function's variables, even after the outer function exits.
+// One of JavaScript's most powerful features is closures. If a function is
+// defined inside another function, the inner function has access to all the
+// outer function's variables, even after the outer function exits.
 function sayHelloInFiveSeconds(name){
     var prompt = "Hello, " + name + "!";
-    // Inner functions are put in the local scope by default, as if they were
-    // declared with `var`.
+    // Inner functions are put in the local scope by default, as if they were
+    // declared with `var`.
     function inner(){
         alert(prompt);
     }
     setTimeout(inner, 5000);
-    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
-    // exit immediately, and setTimeout will call inner afterwards. However,
-    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
-    // access to the `prompt` variable when it is finally called.
+    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
+    // exit immediately, and setTimeout will call inner afterwards. However,
+    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
+    // access to the `prompt` variable when it is finally called.
 }
-sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
+sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
 
-///////////////////////////////////
-// 5. More about Objects; Constructors and Prototypes
+///////////////////////////////////
+// 5. More about Objects; Constructors and Prototypes
 
-// Objects can contain functions.
+// Objects can contain functions.
 var myObj = {
     myFunc: function(){
         return "Hello world!";
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// When functions attached to an object are called, they can access the object
-// they're attached to using the `this` keyword.
+// When functions attached to an object are called, they can access the object
+// they're attached to using the `this` keyword.
 myObj = {
     myString: "Hello world!",
     myFunc: function(){
         return this.myString;
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// What this is set to has to do with how the function is called, not where
-// it's defined. So, our function doesn't work if it isn't called in the
-// context of the object.
+// What this is set to has to do with how the function is called, not where
+// it's defined. So, our function doesn't work if it isn't called in the
+// context of the object.
 var myFunc = myObj.myFunc;
-myFunc(); // = undefined
+myFunc(); // = undefined
 
-// Inversely, a function can be assigned to the object and gain access to it
-// through `this`, even if it wasn't attached when it was defined.
+// Inversely, a function can be assigned to the object and gain access to it
+// through `this`, even if it wasn't attached when it was defined.
 var myOtherFunc = function(){
     return this.myString.toUpperCase();
 };
 myObj.myOtherFunc = myOtherFunc;
-myObj.myOtherFunc(); // = "HELLO WORLD!"
+myObj.myOtherFunc(); // = "HELLO WORLD!"
 
-// We can also specify a context for a function to execute in when we invoke it
-// using `call` or `apply`.
+// We can also specify a context for a function to execute in when we invoke it
+// using `call` or `apply`.
 
 var anotherFunc = function(s){
     return this.myString + s;
 };
-anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
+anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
 
-// The `apply` function is nearly identical, but takes an array for an argument
-// list.
+// The `apply` function is nearly identical, but takes an array for an argument
+// list.
 
-anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
+anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
 
-// This is useful when working with a function that accepts a sequence of
-// arguments and you want to pass an array.
+// This is useful when working with a function that accepts a sequence of
+// arguments and you want to pass an array.
 
-Math.min(42, 6, 27); // = 6
-Math.min([42, 6, 27]); // = NaN (uh-oh!)
-Math.min.apply(Math, [42, 6, 27]); // = 6
+Math.min(42, 6, 27); // = 6
+Math.min([42, 6, 27]); // = NaN (uh-oh!)
+Math.min.apply(Math, [42, 6, 27]); // = 6
 
-// But, `call` and `apply` are only temporary. When we want it to stick, we can
-// use `bind`.
+// But, `call` and `apply` are only temporary. When we want it to stick, we can
+// use `bind`.
 
 var boundFunc = anotherFunc.bind(myObj);
-boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
+boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
 
-// `bind` can also be used to partially apply (curry) a function.
+// `bind` can also be used to partially apply (curry) a function.
 
 var product = function(a, b){ return a * b; };
 var doubler = product.bind(this, 2);
-doubler(8); // = 16
+doubler(8); // = 16
 
-// When you call a function with the `new` keyword, a new object is created, and
-// made available to the function via the `this` keyword. Functions designed to be
-// called like that are called constructors.
+// When you call a function with the `new` keyword, a new object is created, and
+// made available to the function via the `this` keyword. Functions designed to be
+// called like that are called constructors.
 
 var MyConstructor = function(){
     this.myNumber = 5;
 };
-myNewObj = new MyConstructor(); // = {myNumber: 5}
-myNewObj.myNumber; // = 5
+myNewObj = new MyConstructor(); // = {myNumber: 5}
+myNewObj.myNumber; // = 5
 
-// Unlike most other popular object-oriented languages, JavaScript has no
-// concept of 'instances' created from 'class' blueprints; instead, JavaScript
-// combines instantiation and inheritance into a single concept: a 'prototype'.
+// Unlike most other popular object-oriented languages, JavaScript has no
+// concept of 'instances' created from 'class' blueprints; instead, JavaScript
+// combines instantiation and inheritance into a single concept: a 'prototype'.
 
-// Every JavaScript object has a 'prototype'. When you go to access a property
-// on an object that doesn't exist on the actual object, the interpreter will
-// look at its prototype.
+// Every JavaScript object has a 'prototype'. When you go to access a property
+// on an object that doesn't exist on the actual object, the interpreter will
+// look at its prototype.
 
-// Some JS implementations let you access an object's prototype on the magic
-// property `__proto__`. While this is useful for explaining prototypes it's not
-// part of the standard; we'll get to standard ways of using prototypes later.
+// Some JS implementations let you access an object's prototype on the magic
+// property `__proto__`. While this is useful for explaining prototypes it's not
+// part of the standard; we'll get to standard ways of using prototypes later.
 var myObj = {
     myString: "Hello world!"
 };
@@ -459,58 +459,58 @@
 };
 
 myObj.__proto__ = myPrototype;
-myObj.meaningOfLife; // = 42
+myObj.meaningOfLife; // = 42
 
-// This works for functions, too.
-myObj.myFunc(); // = "hello world!"
+// This works for functions, too.
+myObj.myFunc(); // = "hello world!"
 
-// Of course, if your property isn't on your prototype, the prototype's
-// prototype is searched, and so on.
+// Of course, if your property isn't on your prototype, the prototype's
+// prototype is searched, and so on.
 myPrototype.__proto__ = {
     myBoolean: true
 };
-myObj.myBoolean; // = true
+myObj.myBoolean; // = true
 
-// There's no copying involved here; each object stores a reference to its
-// prototype. This means we can alter the prototype and our changes will be
-// reflected everywhere.
+// There's no copying involved here; each object stores a reference to its
+// prototype. This means we can alter the prototype and our changes will be
+// reflected everywhere.
 myPrototype.meaningOfLife = 43;
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The for/in statement allows iteration over properties of an object,
-// walking up the prototype chain until it sees a null prototype.
+// The for/in statement allows iteration over properties of an object,
+// walking up the prototype chain until it sees a null prototype.
 for (var x in myObj){
     console.log(myObj[x]);
 }
-///prints:
-// Hello world!
-// 43
-// [Function: myFunc]
-// true
+///prints:
+// Hello world!
+// 43
+// [Function: myFunc]
+// true
 
-// To only consider properties attached to the object itself
-// and not its prototypes, use the `hasOwnProperty()` check.
+// To only consider properties attached to the object itself
+// and not its prototypes, use the `hasOwnProperty()` check.
 for (var x in myObj){
     if (myObj.hasOwnProperty(x)){
         console.log(myObj[x]);
     }
 }
-///prints:
-// Hello world!
+///prints:
+// Hello world!
 
-// We mentioned that `__proto__` was non-standard, and there's no standard way to
-// change the prototype of an existing object. However, there are two ways to
-// create a new object with a given prototype.
+// We mentioned that `__proto__` was non-standard, and there's no standard way to
+// change the prototype of an existing object. However, there are two ways to
+// create a new object with a given prototype.
 
-// The first is Object.create, which is a recent addition to JS, and therefore
-// not available in all implementations yet.
+// The first is Object.create, which is a recent addition to JS, and therefore
+// not available in all implementations yet.
 var myObj = Object.create(myPrototype);
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The second way, which works anywhere, has to do with constructors.
-// Constructors have a property called prototype. This is *not* the prototype of
-// the constructor function itself; instead, it's the prototype that new objects
-// are given when they're created with that constructor and the new keyword.
+// The second way, which works anywhere, has to do with constructors.
+// Constructors have a property called prototype. This is *not* the prototype of
+// the constructor function itself; instead, it's the prototype that new objects
+// are given when they're created with that constructor and the new keyword.
 MyConstructor.prototype = {
     myNumber: 5,
     getMyNumber: function(){
@@ -518,47 +518,89 @@
     }
 };
 var myNewObj2 = new MyConstructor();
-myNewObj2.getMyNumber(); // = 5
+myNewObj2.getMyNumber(); // = 5
 myNewObj2.myNumber = 6;
-myNewObj2.getMyNumber(); // = 6
+myNewObj2.getMyNumber(); // = 6
 
-// Built-in types like strings and numbers also have constructors that create
-// equivalent wrapper objects.
+// Built-in types like strings and numbers also have constructors that create
+// equivalent wrapper objects.
 var myNumber = 12;
 var myNumberObj = new Number(12);
-myNumber == myNumberObj; // = true
+myNumber == myNumberObj; // = true
 
-// Except, they aren't exactly equivalent.
-typeof myNumber; // = 'number'
-typeof myNumberObj; // = 'object'
-myNumber === myNumberObj; // = false
+// Except, they aren't exactly equivalent.
+typeof myNumber; // = 'number'
+typeof myNumberObj; // = 'object'
+myNumber === myNumberObj; // = false
 if (0){
-    // This code won't execute, because 0 is falsy.
+    // This code won't execute, because 0 is falsy.
 }
 if (new Number(0)){
-   // This code will execute, because wrapped numbers are objects, and objects
-   // are always truthy.
+   // This code will execute, because wrapped numbers are objects, and objects
+   // are always truthy.
 }
 
-// However, the wrapper objects and the regular builtins share a prototype, so
-// you can actually add functionality to a string, for instance.
+// However, the wrapper objects and the regular builtins share a prototype, so
+// you can actually add functionality to a string, for instance.
 String.prototype.firstCharacter = function(){
     return this.charAt(0);
 };
-"abc".firstCharacter(); // = "a"
+"abc".firstCharacter(); // = "a"
 
-// This fact is often used in "polyfilling", which is implementing newer
-// features of JavaScript in an older subset of JavaScript, so that they can be
-// used in older environments such as outdated browsers.
+// This fact is often used in "polyfilling", which is implementing newer
+// features of JavaScript in an older subset of JavaScript, so that they can be
+// used in older environments such as outdated browsers.
 
-// For instance, we mentioned that Object.create isn't yet available in all
-// implementations, but we can still use it with this polyfill:
-if (Object.create === undefined){ // don't overwrite it if it exists
+// For instance, we mentioned that Object.create isn't yet available in all
+// implementations, but we can still use it with this polyfill:
+if (Object.create === undefined){ // don't overwrite it if it exists
     Object.create = function(proto){
-        // make a temporary constructor with the right prototype
+        // make a temporary constructor with the right prototype
         var Constructor = function(){};
         Constructor.prototype = proto;
-        // then use it to create a new, appropriately-prototyped object
+        // then use it to create a new, appropriately-prototyped object
         return new Constructor();
     };
 }
+
+// ES6 Additions
+
+// The "let" keyword allows you to define variables in a lexical scope, 
+// as opposed to a block scope like the var keyword does.
+let name = "Billy";
+
+// Variables defined with let can be reassigned new values.
+name = "William";
+
+// The "const" keyword allows you to define a variable in a lexical scope
+// like with let, but you cannot reassign the value once one has been assigned.
+
+const pi = 3.14;
+
+pi = 4.13; // You cannot do this.
+
+// There is a new syntax for functions in ES6 known as "lambda syntax".
+// This allows functions to be defined in a lexical scope like with variables
+// defined by const and let. 
+
+const isEven = (number) => {
+    return number % 2 === 0;
+};
+
+isEven(7); // false
+
+// The "equivalent" of this function in the traditional syntax would look like this:
+
+function isEven(number) {
+    return number % 2 === 0;
+};
+
+// I put the word "equivalent" in double quotes because a function defined
+// using the lambda syntax cannnot be called before the definition.
+// The following is an example of invalid usage:
+
+add(1, 8);
+
+const add = (firstNumber, secondNumber) => {
+    return firstNumber + secondNumber;
+};

tests/results/22

@@ -1,270 +1,270 @@
-// Single-line comments start with two slashes.
-/* Multiline comments start with slash-star,
-   and end with star-slash */
+// Single-line comments start with two slashes.
+/* Multiline comments start with slash-star,
+   and end with star-slash */
 
-// Statements can be terminated by ;
+// Statements can be terminated by ;
 doStuff();
 
-// ... but they don't have to be, as semicolons are automatically inserted
-// wherever there's a newline, except in certain cases.
+// ... but they don't have to be, as semicolons are automatically inserted
+// wherever there's a newline, except in certain cases.
 doStuff()
 
-// Because those cases can cause unexpected results, we'll keep on using
-// semicolons in this guide.
+// Because those cases can cause unexpected results, we'll keep on using
+// semicolons in this guide.
 
-///////////////////////////////////
-// 1. Numbers, Strings and Operators
+///////////////////////////////////
+// 1. Numbers, Strings and Operators
 
-// JavaScript has one number type (which is a 64-bit IEEE 754 double).
-// Doubles have a 52-bit mantissa, which is enough to store integers
-// up to about 9✕10¹⁵ precisely.
-3; // = 3
-1.5; // = 1.5
+// JavaScript has one number type (which is a 64-bit IEEE 754 double).
+// Doubles have a 52-bit mantissa, which is enough to store integers
+// up to about 9✕10¹⁵ precisely.
+3; // = 3
+1.5; // = 1.5
 
-// Some basic arithmetic works as you'd expect.
-1 + 1; // = 2
-0.1 + 0.2; // = 0.30000000000000004
-8 - 1; // = 7
-10 * 2; // = 20
-35 / 5; // = 7
+// Some basic arithmetic works as you'd expect.
+1 + 1; // = 2
+0.1 + 0.2; // = 0.30000000000000004
+8 - 1; // = 7
+10 * 2; // = 20
+35 / 5; // = 7
 
-// Including uneven division.
-5 / 2; // = 2.5
+// Including uneven division.
+5 / 2; // = 2.5
 
-// And modulo division.
-10 % 2; // = 0
-30 % 4; // = 2
-18.5 % 7; // = 4.5
+// And modulo division.
+10 % 2; // = 0
+30 % 4; // = 2
+18.5 % 7; // = 4.5
 
-// Bitwise operations also work; when you perform a bitwise operation your float
-// is converted to a signed int *up to* 32 bits.
-1 << 2; // = 4
+// Bitwise operations also work; when you perform a bitwise operation your float
+// is converted to a signed int *up to* 32 bits.
+1 << 2; // = 4
 
-// Precedence is enforced with parentheses.
-(1 + 3) * 2; // = 8
+// Precedence is enforced with parentheses.
+(1 + 3) * 2; // = 8
 
-// There are three special not-a-real-number values:
-Infinity; // result of e.g. 1/0
--Infinity; // result of e.g. -1/0
-NaN; // result of e.g. 0/0, stands for 'Not a Number'
+// There are three special not-a-real-number values:
+Infinity; // result of e.g. 1/0
+-Infinity; // result of e.g. -1/0
+NaN; // result of e.g. 0/0, stands for 'Not a Number'
 
-// There's also a boolean type.
+// There's also a boolean type.
 true;
 false;
 
-// Strings are created with ' or ".
+// Strings are created with ' or ".
 'abc';
 "Hello, world";
 
-// Negation uses the ! symbol
-!true; // = false
-!false; // = true
+// Negation uses the ! symbol
+!true; // = false
+!false; // = true
 
-// Equality is ===
-1 === 1; // = true
-2 === 1; // = false
+// Equality is ===
+1 === 1; // = true
+2 === 1; // = false
 
-// Inequality is !==
-1 !== 1; // = false
-2 !== 1; // = true
+// Inequality is !==
+1 !== 1; // = false
+2 !== 1; // = true
 
-// More comparisons
-1 < 10; // = true
-1 > 10; // = false
-2 <= 2; // = true
-2 >= 2; // = true
+// More comparisons
+1 < 10; // = true
+1 > 10; // = false
+2 <= 2; // = true
+2 >= 2; // = true
 
-// Strings are concatenated with +
-"Hello " + "world!"; // = "Hello world!"
+// Strings are concatenated with +
+"Hello " + "world!"; // = "Hello world!"
 
-// ... which works with more than just strings
-"1, 2, " + 3; // = "1, 2, 3"
-"Hello " + ["world", "!"]; // = "Hello world,!"
+// ... which works with more than just strings
+"1, 2, " + 3; // = "1, 2, 3"
+"Hello " + ["world", "!"]; // = "Hello world,!"
 
-// and are compared with < and >
-"a" < "b"; // = true
+// and are compared with < and >
+"a" < "b"; // = true
 
-// Type coercion is performed for comparisons with double equals...
-"5" == 5; // = true
-null == undefined; // = true
+// Type coercion is performed for comparisons with double equals...
+"5" == 5; // = true
+null == undefined; // = true
 
-// ...unless you use ===
-"5" === 5; // = false
-null === undefined; // = false
+// ...unless you use ===
+"5" === 5; // = false
+null === undefined; // = false
 
-// ...which can result in some weird behaviour...
-13 + !0; // 14
-"13" + !0; // '13true'
+// ...which can result in some weird behaviour...
+13 + !0; // 14
+"13" + !0; // '13true'
 
-// You can access characters in a string with `charAt`
-"This is a string".charAt(0);  // = 'T'
+// You can access characters in a string with `charAt`
+"This is a string".charAt(0);  // = 'T'
 
-// ...or use `substring` to get larger pieces.
-"Hello world".substring(0, 5); // = "Hello"
+// ...or use `substring` to get larger pieces.
+"Hello world".substring(0, 5); // = "Hello"
 
-// `length` is a property, so don't use ().
-"Hello".length; // = 5
+// `length` is a property, so don't use ().
+"Hello".length; // = 5
 
-// There's also `null` and `undefined`.
-null;      // used to indicate a deliberate non-value
-undefined; // used to indicate a value is not currently present (although
-           // `undefined` is actually a value itself)
+// There's also `null` and `undefined`.
+null;      // used to indicate a deliberate non-value
+undefined; // used to indicate a value is not currently present (although
+           // `undefined` is actually a value itself)
 
-// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
-// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
+// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
+// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
 
-///////////////////////////////////
-// 2. Variables, Arrays and Objects
+///////////////////////////////////
+// 2. Variables, Arrays and Objects
 
-// Variables are declared with the `var` keyword. JavaScript is dynamically
-// typed, so you don't need to specify type. Assignment uses a single `=`
-// character.
+// Variables are declared with the `var` keyword. JavaScript is dynamically
+// typed, so you don't need to specify type. Assignment uses a single `=`
+// character.
 var someVar = 5;
 
-// If you leave the var keyword off, you won't get an error...
+// If you leave the var keyword off, you won't get an error...
 someOtherVar = 10;
 
-// ...but your variable will be created in the global scope, not in the scope
-// you defined it in.
+// ...but your variable will be created in the global scope, not in the scope
+// you defined it in.
 
-// Variables declared without being assigned to are set to undefined.
-var someThirdVar; // = undefined
+// Variables declared without being assigned to are set to undefined.
+var someThirdVar; // = undefined
 
-// If you want to declare a couple of variables, then you could use a comma
-// separator
+// If you want to declare a couple of variables, then you could use a comma
+// separator
 var someFourthVar = 2, someFifthVar = 4;
 
-// There's shorthand for performing math operations on variables:
-someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
-someVar *= 10; // now someVar is 100
+// There's shorthand for performing math operations on variables:
+someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
+someVar *= 10; // now someVar is 100
 
-// and an even-shorter-hand for adding or subtracting 1
-someVar++; // now someVar is 101
-someVar--; // back to 100
+// and an even-shorter-hand for adding or subtracting 1
+someVar++; // now someVar is 101
+someVar--; // back to 100
 
-// Arrays are ordered lists of values, of any type.
+// Arrays are ordered lists of values, of any type.
 var myArray = ["Hello", 45, true];
 
-// Their members can be accessed using the square-brackets subscript syntax.
-// Array indices start at zero.
-myArray[1]; // = 45
+// Their members can be accessed using the square-brackets subscript syntax.
+// Array indices start at zero.
+myArray[1]; // = 45
 
-// Arrays are mutable and of variable length.
+// Arrays are mutable and of variable length.
 myArray.push("World");
-myArray.length; // = 4
+myArray.length; // = 4
 
-// Add/Modify at specific index
+// Add/Modify at specific index
 myArray[3] = "Hello";
 
-// Add and remove element from front or back end of an array
-myArray.unshift(3); // Add as the first element
-someVar = myArray.shift(); // Remove first element and return it
-myArray.push(3); // Add as the last element
-someVar = myArray.pop(); // Remove last element and return it
+// Add and remove element from front or back end of an array
+myArray.unshift(3); // Add as the first element
+someVar = myArray.shift(); // Remove first element and return it
+myArray.push(3); // Add as the last element
+someVar = myArray.pop(); // Remove last element and return it
 
-// Join all elements of an array with semicolon
+// Join all elements of an array with semicolon
 var myArray0 = [32,false,"js",12,56,90];
-myArray0.join(";") // = "32;false;js;12;56;90"
+myArray0.join(";"); // = "32;false;js;12;56;90"
 
-// Get subarray of elements from index 1 (include) to 4 (exclude)
-myArray0.slice(1,4); // = [false,"js",12]
+// Get subarray of elements from index 1 (include) to 4 (exclude)
+myArray0.slice(1,4); // = [false,"js",12]
 
-// Remove 4 elements starting from index 2, and insert there strings
-// "hi","wr" and "ld"; return removed subarray
-myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
-// myArray0 === [32,false,"hi","wr","ld"]
+// Remove 4 elements starting from index 2, and insert there strings
+// "hi","wr" and "ld"; return removed subarray
+myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
+// myArray0 === [32,false,"hi","wr","ld"]
 
-// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
-// languages: an unordered collection of key-value pairs.
+// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
+// languages: an unordered collection of key-value pairs.
 var myObj = {key1: "Hello", key2: "World"};
 
-// Keys are strings, but quotes aren't required if they're a valid
-// JavaScript identifier. Values can be any type.
+// Keys are strings, but quotes aren't required if they're a valid
+// JavaScript identifier. Values can be any type.
 var myObj = {myKey: "myValue", "my other key": 4};
 
-// Object attributes can also be accessed using the subscript syntax,
-myObj["my other key"]; // = 4
+// Object attributes can also be accessed using the subscript syntax,
+myObj["my other key"]; // = 4
 
-// ... or using the dot syntax, provided the key is a valid identifier.
-myObj.myKey; // = "myValue"
+// ... or using the dot syntax, provided the key is a valid identifier.
+myObj.myKey; // = "myValue"
 
-// Objects are mutable; values can be changed and new keys added.
+// Objects are mutable; values can be changed and new keys added.
 myObj.myThirdKey = true;
 
-// If you try to access a value that's not yet set, you'll get undefined.
-myObj.myFourthKey; // = undefined
+// If you try to access a value that's not yet set, you'll get undefined.
+myObj.myFourthKey; // = undefined
 
-///////////////////////////////////
-// 3. Logic and Control Structures
+///////////////////////////////////
+// 3. Logic and Control Structures
 
-// The `if` structure works as you'd expect.
+// The `if` structure works as you'd expect.
 var count = 1;
 if (count == 3){
-    // evaluated if count is 3
+    // evaluated if count is 3
 } else if (count == 4){
-    // evaluated if count is 4
+    // evaluated if count is 4
 } else {
-    // evaluated if it's not either 3 or 4
+    // evaluated if it's not either 3 or 4
 }
 
-// As does `while`.
+// As does `while`.
 while (true){
-    // An infinite loop!
+    // An infinite loop!
 }
 
-// Do-while loops are like while loops, except they always run at least once.
+// Do-while loops are like while loops, except they always run at least once.
 var input;
 do {
     input = getInput();
 } while (!isValid(input));
 
-// The `for` loop is the same as C and Java:
-// initialization; continue condition; iteration.
+// The `for` loop is the same as C and Java:
+// initialization; continue condition; iteration.
 for (var i = 0; i < 5; i++){
-    // will run 5 times
+    // will run 5 times
 }
 
-// Breaking out of labeled loops is similar to Java
+// Breaking out of labeled loops is similar to Java
 outer:
 for (var i = 0; i < 10; i++) {
     for (var j = 0; j < 10; j++) {
         if (i == 5 && j ==5) {
             break outer;
-            // breaks out of outer loop instead of only the inner one
+            // breaks out of outer loop instead of only the inner one
         }
     }
 }
 
-// The for/in statement allows iteration over properties of an object.
+// The for/in statement allows iteration over properties of an object.
 var description = "";
 var person = {fname:"Paul", lname:"Ken", age:18};
 for (var x in person){
     description += person[x] + " ";
-} // description = 'Paul Ken 18 '
+} // description = 'Paul Ken 18 '
 
-// The for/of statement allows iteration over iterable objects (including the built-in String, 
-// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
-// and user-defined iterables).
+// The for/of statement allows iteration over iterable objects (including the built-in String, 
+// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
+// and user-defined iterables).
 var myPets = "";
 var pets = ["cat", "dog", "hamster", "hedgehog"];
 for (var pet of pets){
     myPets += pet + " ";
-} // myPets = 'cat dog hamster hedgehog '
+} // myPets = 'cat dog hamster hedgehog '
 
-// && is logical and, || is logical or
+// && is logical and, || is logical or
 if (house.size == "big" && house.colour == "blue"){
     house.contains = "bear";
 }
 if (colour == "red" || colour == "blue"){
-    // colour is either red or blue
+    // colour is either red or blue
 }
 
-// && and || "short circuit", which is useful for setting default values.
+// && and || "short circuit", which is useful for setting default values.
 var name = otherName || "default";
 
-// The `switch` statement checks for equality with `===`.
-// Use 'break' after each case
-// or the cases after the correct one will be executed too.
+// The `switch` statement checks for equality with `===`.
+// Use 'break' after each case
+// or the cases after the correct one will be executed too.
 grade = 'B';
 switch (grade) {
   case 'A':
@@ -282,172 +282,172 @@
 }
 
 
-///////////////////////////////////
-// 4. Functions, Scope and Closures
+///////////////////////////////////
+// 4. Functions, Scope and Closures
 
-// JavaScript functions are declared with the `function` keyword.
+// JavaScript functions are declared with the `function` keyword.
 function myFunction(thing){
     return thing.toUpperCase();
 }
-myFunction("foo"); // = "FOO"
+myFunction("foo"); // = "FOO"
 
-// Note that the value to be returned must start on the same line as the
-// `return` keyword, otherwise you'll always return `undefined` due to
-// automatic semicolon insertion. Watch out for this when using Allman style.
+// Note that the value to be returned must start on the same line as the
+// `return` keyword, otherwise you'll always return `undefined` due to
+// automatic semicolon insertion. Watch out for this when using Allman style.
 function myFunction(){
-    return // <- semicolon automatically inserted here
+    return // <- semicolon automatically inserted here
     {thisIsAn: 'object literal'};
 }
-myFunction(); // = undefined
+myFunction(); // = undefined
 
-// JavaScript functions are first class objects, so they can be reassigned to
-// different variable names and passed to other functions as arguments - for
-// example, when supplying an event handler:
+// JavaScript functions are first class objects, so they can be reassigned to
+// different variable names and passed to other functions as arguments - for
+// example, when supplying an event handler:
 function myFunction(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }
 setTimeout(myFunction, 5000);
-// Note: setTimeout isn't part of the JS language, but is provided by browsers
-// and Node.js.
+// Note: setTimeout isn't part of the JS language, but is provided by browsers
+// and Node.js.
 
-// Another function provided by browsers is setInterval
+// Another function provided by browsers is setInterval
 function myFunction(){
-    // this code will be called every 5 seconds
+    // this code will be called every 5 seconds
 }
 setInterval(myFunction, 5000);
 
-// Function objects don't even have to be declared with a name - you can write
-// an anonymous function definition directly into the arguments of another.
+// Function objects don't even have to be declared with a name - you can write
+// an anonymous function definition directly into the arguments of another.
 setTimeout(function(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }, 5000);
 
-// JavaScript has function scope; functions get their own scope but other blocks
-// do not.
+// JavaScript has function scope; functions get their own scope but other blocks
+// do not.
 if (true){
     var i = 5;
 }
-i; // = 5 - not undefined as you'd expect in a block-scoped language
+i; // = 5 - not undefined as you'd expect in a block-scoped language
 
-// This has led to a common pattern of "immediately-executing anonymous
-// functions", which prevent temporary variables from leaking into the global
-// scope.
+// This has led to a common pattern of "immediately-executing anonymous
+// functions", which prevent temporary variables from leaking into the global
+// scope.
 (function(){
     var temporary = 5;
-    // We can access the global scope by assigning to the "global object", which
-    // in a web browser is always `window`. The global object may have a
-    // different name in non-browser environments such as Node.js.
+    // We can access the global scope by assigning to the "global object", which
+    // in a web browser is always `window`. The global object may have a
+    // different name in non-browser environments such as Node.js.
     window.permanent = 10;
 })();
-temporary; // raises ReferenceError
-permanent; // = 10
+temporary; // raises ReferenceError
+permanent; // = 10
 
-// One of JavaScript's most powerful features is closures. If a function is
-// defined inside another function, the inner function has access to all the
-// outer function's variables, even after the outer function exits.
+// One of JavaScript's most powerful features is closures. If a function is
+// defined inside another function, the inner function has access to all the
+// outer function's variables, even after the outer function exits.
 function sayHelloInFiveSeconds(name){
     var prompt = "Hello, " + name + "!";
-    // Inner functions are put in the local scope by default, as if they were
-    // declared with `var`.
+    // Inner functions are put in the local scope by default, as if they were
+    // declared with `var`.
     function inner(){
         alert(prompt);
     }
     setTimeout(inner, 5000);
-    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
-    // exit immediately, and setTimeout will call inner afterwards. However,
-    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
-    // access to the `prompt` variable when it is finally called.
+    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
+    // exit immediately, and setTimeout will call inner afterwards. However,
+    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
+    // access to the `prompt` variable when it is finally called.
 }
-sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
+sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
 
-///////////////////////////////////
-// 5. More about Objects; Constructors and Prototypes
+///////////////////////////////////
+// 5. More about Objects; Constructors and Prototypes
 
-// Objects can contain functions.
+// Objects can contain functions.
 var myObj = {
     myFunc: function(){
         return "Hello world!";
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// When functions attached to an object are called, they can access the object
-// they're attached to using the `this` keyword.
+// When functions attached to an object are called, they can access the object
+// they're attached to using the `this` keyword.
 myObj = {
     myString: "Hello world!",
     myFunc: function(){
         return this.myString;
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// What this is set to has to do with how the function is called, not where
-// it's defined. So, our function doesn't work if it isn't called in the
-// context of the object.
+// What this is set to has to do with how the function is called, not where
+// it's defined. So, our function doesn't work if it isn't called in the
+// context of the object.
 var myFunc = myObj.myFunc;
-myFunc(); // = undefined
+myFunc(); // = undefined
 
-// Inversely, a function can be assigned to the object and gain access to it
-// through `this`, even if it wasn't attached when it was defined.
+// Inversely, a function can be assigned to the object and gain access to it
+// through `this`, even if it wasn't attached when it was defined.
 var myOtherFunc = function(){
     return this.myString.toUpperCase();
 };
 myObj.myOtherFunc = myOtherFunc;
-myObj.myOtherFunc(); // = "HELLO WORLD!"
+myObj.myOtherFunc(); // = "HELLO WORLD!"
 
-// We can also specify a context for a function to execute in when we invoke it
-// using `call` or `apply`.
+// We can also specify a context for a function to execute in when we invoke it
+// using `call` or `apply`.
 
 var anotherFunc = function(s){
     return this.myString + s;
 };
-anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
+anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
 
-// The `apply` function is nearly identical, but takes an array for an argument
-// list.
+// The `apply` function is nearly identical, but takes an array for an argument
+// list.
 
-anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
+anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
 
-// This is useful when working with a function that accepts a sequence of
-// arguments and you want to pass an array.
+// This is useful when working with a function that accepts a sequence of
+// arguments and you want to pass an array.
 
-Math.min(42, 6, 27); // = 6
-Math.min([42, 6, 27]); // = NaN (uh-oh!)
-Math.min.apply(Math, [42, 6, 27]); // = 6
+Math.min(42, 6, 27); // = 6
+Math.min([42, 6, 27]); // = NaN (uh-oh!)
+Math.min.apply(Math, [42, 6, 27]); // = 6
 
-// But, `call` and `apply` are only temporary. When we want it to stick, we can
-// use `bind`.
+// But, `call` and `apply` are only temporary. When we want it to stick, we can
+// use `bind`.
 
 var boundFunc = anotherFunc.bind(myObj);
-boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
+boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
 
-// `bind` can also be used to partially apply (curry) a function.
+// `bind` can also be used to partially apply (curry) a function.
 
 var product = function(a, b){ return a * b; };
 var doubler = product.bind(this, 2);
-doubler(8); // = 16
+doubler(8); // = 16
 
-// When you call a function with the `new` keyword, a new object is created, and
-// made available to the function via the `this` keyword. Functions designed to be
-// called like that are called constructors.
+// When you call a function with the `new` keyword, a new object is created, and
+// made available to the function via the `this` keyword. Functions designed to be
+// called like that are called constructors.
 
 var MyConstructor = function(){
     this.myNumber = 5;
 };
-myNewObj = new MyConstructor(); // = {myNumber: 5}
-myNewObj.myNumber; // = 5
+myNewObj = new MyConstructor(); // = {myNumber: 5}
+myNewObj.myNumber; // = 5
 
-// Unlike most other popular object-oriented languages, JavaScript has no
-// concept of 'instances' created from 'class' blueprints; instead, JavaScript
-// combines instantiation and inheritance into a single concept: a 'prototype'.
+// Unlike most other popular object-oriented languages, JavaScript has no
+// concept of 'instances' created from 'class' blueprints; instead, JavaScript
+// combines instantiation and inheritance into a single concept: a 'prototype'.
 
-// Every JavaScript object has a 'prototype'. When you go to access a property
-// on an object that doesn't exist on the actual object, the interpreter will
-// look at its prototype.
+// Every JavaScript object has a 'prototype'. When you go to access a property
+// on an object that doesn't exist on the actual object, the interpreter will
+// look at its prototype.
 
-// Some JS implementations let you access an object's prototype on the magic
-// property `__proto__`. While this is useful for explaining prototypes it's not
-// part of the standard; we'll get to standard ways of using prototypes later.
+// Some JS implementations let you access an object's prototype on the magic
+// property `__proto__`. While this is useful for explaining prototypes it's not
+// part of the standard; we'll get to standard ways of using prototypes later.
 var myObj = {
     myString: "Hello world!"
 };
@@ -459,58 +459,58 @@
 };
 
 myObj.__proto__ = myPrototype;
-myObj.meaningOfLife; // = 42
+myObj.meaningOfLife; // = 42
 
-// This works for functions, too.
-myObj.myFunc(); // = "hello world!"
+// This works for functions, too.
+myObj.myFunc(); // = "hello world!"
 
-// Of course, if your property isn't on your prototype, the prototype's
-// prototype is searched, and so on.
+// Of course, if your property isn't on your prototype, the prototype's
+// prototype is searched, and so on.
 myPrototype.__proto__ = {
     myBoolean: true
 };
-myObj.myBoolean; // = true
+myObj.myBoolean; // = true
 
-// There's no copying involved here; each object stores a reference to its
-// prototype. This means we can alter the prototype and our changes will be
-// reflected everywhere.
+// There's no copying involved here; each object stores a reference to its
+// prototype. This means we can alter the prototype and our changes will be
+// reflected everywhere.
 myPrototype.meaningOfLife = 43;
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The for/in statement allows iteration over properties of an object,
-// walking up the prototype chain until it sees a null prototype.
+// The for/in statement allows iteration over properties of an object,
+// walking up the prototype chain until it sees a null prototype.
 for (var x in myObj){
     console.log(myObj[x]);
 }
-///prints:
-// Hello world!
-// 43
-// [Function: myFunc]
-// true
+///prints:
+// Hello world!
+// 43
+// [Function: myFunc]
+// true
 
-// To only consider properties attached to the object itself
-// and not its prototypes, use the `hasOwnProperty()` check.
+// To only consider properties attached to the object itself
+// and not its prototypes, use the `hasOwnProperty()` check.
 for (var x in myObj){
     if (myObj.hasOwnProperty(x)){
         console.log(myObj[x]);
     }
 }
-///prints:
-// Hello world!
+///prints:
+// Hello world!
 
-// We mentioned that `__proto__` was non-standard, and there's no standard way to
-// change the prototype of an existing object. However, there are two ways to
-// create a new object with a given prototype.
+// We mentioned that `__proto__` was non-standard, and there's no standard way to
+// change the prototype of an existing object. However, there are two ways to
+// create a new object with a given prototype.
 
-// The first is Object.create, which is a recent addition to JS, and therefore
-// not available in all implementations yet.
+// The first is Object.create, which is a recent addition to JS, and therefore
+// not available in all implementations yet.
 var myObj = Object.create(myPrototype);
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The second way, which works anywhere, has to do with constructors.
-// Constructors have a property called prototype. This is *not* the prototype of
-// the constructor function itself; instead, it's the prototype that new objects
-// are given when they're created with that constructor and the new keyword.
+// The second way, which works anywhere, has to do with constructors.
+// Constructors have a property called prototype. This is *not* the prototype of
+// the constructor function itself; instead, it's the prototype that new objects
+// are given when they're created with that constructor and the new keyword.
 MyConstructor.prototype = {
     myNumber: 5,
     getMyNumber: function(){
@@ -518,47 +518,89 @@
     }
 };
 var myNewObj2 = new MyConstructor();
-myNewObj2.getMyNumber(); // = 5
+myNewObj2.getMyNumber(); // = 5
 myNewObj2.myNumber = 6;
-myNewObj2.getMyNumber(); // = 6
+myNewObj2.getMyNumber(); // = 6
 
-// Built-in types like strings and numbers also have constructors that create
-// equivalent wrapper objects.
+// Built-in types like strings and numbers also have constructors that create
+// equivalent wrapper objects.
 var myNumber = 12;
 var myNumberObj = new Number(12);
-myNumber == myNumberObj; // = true
+myNumber == myNumberObj; // = true
 
-// Except, they aren't exactly equivalent.
-typeof myNumber; // = 'number'
-typeof myNumberObj; // = 'object'
-myNumber === myNumberObj; // = false
+// Except, they aren't exactly equivalent.
+typeof myNumber; // = 'number'
+typeof myNumberObj; // = 'object'
+myNumber === myNumberObj; // = false
 if (0){
-    // This code won't execute, because 0 is falsy.
+    // This code won't execute, because 0 is falsy.
 }
 if (new Number(0)){
-   // This code will execute, because wrapped numbers are objects, and objects
-   // are always truthy.
+   // This code will execute, because wrapped numbers are objects, and objects
+   // are always truthy.
 }
 
-// However, the wrapper objects and the regular builtins share a prototype, so
-// you can actually add functionality to a string, for instance.
+// However, the wrapper objects and the regular builtins share a prototype, so
+// you can actually add functionality to a string, for instance.
 String.prototype.firstCharacter = function(){
     return this.charAt(0);
 };
-"abc".firstCharacter(); // = "a"
+"abc".firstCharacter(); // = "a"
 
-// This fact is often used in "polyfilling", which is implementing newer
-// features of JavaScript in an older subset of JavaScript, so that they can be
-// used in older environments such as outdated browsers.
+// This fact is often used in "polyfilling", which is implementing newer
+// features of JavaScript in an older subset of JavaScript, so that they can be
+// used in older environments such as outdated browsers.
 
-// For instance, we mentioned that Object.create isn't yet available in all
-// implementations, but we can still use it with this polyfill:
-if (Object.create === undefined){ // don't overwrite it if it exists
+// For instance, we mentioned that Object.create isn't yet available in all
+// implementations, but we can still use it with this polyfill:
+if (Object.create === undefined){ // don't overwrite it if it exists
     Object.create = function(proto){
-        // make a temporary constructor with the right prototype
+        // make a temporary constructor with the right prototype
         var Constructor = function(){};
         Constructor.prototype = proto;
-        // then use it to create a new, appropriately-prototyped object
+        // then use it to create a new, appropriately-prototyped object
         return new Constructor();
     };
 }
+
+// ES6 Additions
+
+// The "let" keyword allows you to define variables in a lexical scope, 
+// as opposed to a block scope like the var keyword does.
+let name = "Billy";
+
+// Variables defined with let can be reassigned new values.
+name = "William";
+
+// The "const" keyword allows you to define a variable in a lexical scope
+// like with let, but you cannot reassign the value once one has been assigned.
+
+const pi = 3.14;
+
+pi = 4.13; // You cannot do this.
+
+// There is a new syntax for functions in ES6 known as "lambda syntax".
+// This allows functions to be defined in a lexical scope like with variables
+// defined by const and let. 
+
+const isEven = (number) => {
+    return number % 2 === 0;
+};
+
+isEven(7); // false
+
+// The "equivalent" of this function in the traditional syntax would look like this:
+
+function isEven(number) {
+    return number % 2 === 0;
+};
+
+// I put the word "equivalent" in double quotes because a function defined
+// using the lambda syntax cannnot be called before the definition.
+// The following is an example of invalid usage:
+
+add(1, 8);
+
+const add = (firstNumber, secondNumber) => {
+    return firstNumber + secondNumber;
+};

tests/results/3

@@ -1,17 +1,17 @@
-# Displays everything in the target directory
-ls path/to/the/target/directory
+# To display everything in <dir>, excluding hidden files:
+ls <dir>
 
-# Displays everything including hidden files
-ls -a
+# To display everything in <dir>, including hidden files:
+ls -a <dir>
 
-# Displays all files, along with the size (with unit suffixes) and timestamp
-ls -lh 
+# To display all files, along with the size (with unit suffixes) and timestamp
+ls -lh <dir>
 
-# Display files, sorted by size
-ls -S
+# To display files, sorted by size:
+ls -S <dir>
 
-# Display directories only
-ls -d */
+# To display directories only:
+ls -d */ <dir>
 
-# Display directories only, include hidden
-ls -d .*/ */
+# To display directories only, include hidden:
+ls -d .*/ */ <dir>

tests/results/4

@@ -1,54 +1,54 @@
-# Create a btrfs file system on /dev/sdb, /dev/sdc, and /dev/sdd
+# Create a btrfs file system on /dev/sdb, /dev/sdc, and /dev/sdd
 mkfs.btrfs /dev/sdb /dev/sdc /dev/sdd
 
-# btrfs with just one hard drive, metadata not redundant
-# (this is danegerous: if your metadata is lost, your data is lost as well)
+# btrfs with just one hard drive, metadata not redundant
+# (this is danegerous: if your metadata is lost, your data is lost as well)
 mkfs.btrfs -m single /dev/sdb
 
-# data to be redundant and metadata to be non-redundant:
+# data to be redundant and metadata to be non-redundant:
 mkfs.btrfs -m raid0 -d raid1 /dev/sdb /dev/sdc /dev/sdd
 
-# both data and metadata to be redundan
+# both data and metadata to be redundan
 mkfs.btrfs -d raid1 /dev/sdb /dev/sdc /dev/sdd
 
-# To get a list of all btrfs file systems
+# To get a list of all btrfs file systems
 btrfs filesystem show
 
-# detailed df for a fileesystem (mounted in /mnt)
+# detailed df for a fileesystem (mounted in /mnt)
 btrfs filesystem df /mnt
 
-# resize btrfs online (-2g decreases, +2g increases)
+# resize btrfs online (-2g decreases, +2g increases)
 btrfs filesystem resize -2g /mnt
 
-# use maximum space
+# use maximum space
 btrfs filesystem resize max /mnt
 
-# add new device to a filesystem
+# add new device to a filesystem
 btrfs device add /dev/sdf /mnt
 
-# remove devices from a filesystem
+# remove devices from a filesystem
 btrfs device delete missing /mnt
 
-# create the subvolume /mnt/sv1 in the /mnt volume
+# create the subvolume /mnt/sv1 in the /mnt volume
 btrfs subvolume create /mnt/sv1
 
-# list subvolumes
+# list subvolumes
 btrfs subvolume list /mnt
 
-# mount subvolume without mounting the main filesystem
+# mount subvolume without mounting the main filesystem
 mount -o subvol=sv1 /dev/sdb /mnt
 
-# delete subvolume
+# delete subvolume
 btrfs subvolume delete /mnt/sv1
 
-# taking snapshot of a subvolume
+# taking snapshot of a subvolume
 btrfs subvolume snapshot /mnt/sv1 /mnt/sv1_snapshot
 
-# taking snapshot of a file (copy file by reference)
+# taking snapshot of a file (copy file by reference)
 cp --reflink /mnt/sv1/test1 /mnt/sv1/test3
 
-# convert ext3/ext4 to btrfs
+# convert ext3/ext4 to btrfs
 btrfs-convert /dev/sdb1
 
-# convert btrfs to ext3/ext4
+# convert btrfs to ext3/ext4
 btrfs-convert -r /dev/sdb1

tests/results/5

@@ -1,3 +1,3 @@
  btrfs 
-# create the subvolume /mnt/sv1 in the /mnt volume
+# create the subvolume /mnt/sv1 in the /mnt volume
 btrfs subvolume create /mnt/sv1

tests/run-tests.sh

@@ -25,6 +25,7 @@ echo "Using PYTHON $python_version: $PYTHON"
 skip_online="${CHEATSH_TEST_SKIP_ONLINE:-NO}"
 test_standalone="${CHEATSH_TEST_STANDALONE:-YES}"
 show_details="${CHEATSH_TEST_SHOW_DETAILS:-YES}"
+update_tests_results="${CHEATSH_UPDATE_TESTS_RESULTS:-NO}"
 CHTSH_URL="${CHTSH_URL:-http://localhost:8002}"
 
 TMP=$(mktemp /tmp/cht.sh.tests-XXXXXXXXXXXXXX)
@@ -83,19 +84,29 @@ while read -r number test_line; do
   fi
 
   if ! diff -u3 --color=always results/"$number" "$TMP" > "$TMP2"; then
-    if [ "$show_details" = YES ]; then
-      cat "$TMP2"
+    if [[ $CHEATSH_UPDATE_TESTS_RESULTS = NO ]]; then
+      if [ "$show_details" = YES ]; then
+        echo "$ CHEATSH_CACHE_TYPE=none python ../lib/standalone.py $test_line"
+        cat "$TMP2"
+      fi
+      if grep -q "Internal Server Error" "$TMP2"; then
+        [[ $TRAVIS == true ]] && docker logs chtsh
+      fi
+      echo "FAILED: [$number] $test_line"
+    else
+      cat "$TMP" > results/"$number"
+      echo "UPDATED: [$number] $test_line"
     fi
-    if grep -q "Internal Server Error" "$TMP2"; then
-      [[ $TRAVIS == true ]] && docker logs chtsh
-    fi
-    echo "FAILED: [$number] $test_line"
     ((failed++))
   fi
   ((i++))
 done < "$TMP3"
 
-echo TESTS/OK/FAILED "$i/$((i-failed))/$failed"
+if [[ $CHEATSH_UPDATE_TESTS_RESULTS = NO ]]; then
+  echo TESTS/OK/FAILED "$i/$((i-failed))/$failed"
+else
+  echo TESTS/OK/UPDATED "$i/$((i-failed))/$failed"
+fi
 
 if [ "$failed" != 0 ]; then
   exit 1