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javascript/en: added some md formatting
Added some markdown formatting to the comments throughout to clarify meaning. Also tweaked a couple of other quote marks as well. Also shortened a couple of long lines. More to do, but stopped here for now. :)
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@ -110,19 +110,19 @@ null === undefined; // = false
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13 + !0; // 14
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"13" + !0; // '13true'
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// You can access characters in a string with charAt
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// You can access characters in a string with `charAt`
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"This is a string".charAt(0); // = 'T'
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// ...or use substring to get larger pieces
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// ...or use `substring` to get larger pieces.
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"Hello world".substring(0, 5); // = "Hello"
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// length is a property, so don't use ()
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// `length` is a property, so don't use ().
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"Hello".length; // = 5
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// There's also null and undefined
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null; // used to indicate a deliberate non-value
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// There's also `null` and `undefined`.
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null; // used to indicate a deliberate non-value
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undefined; // used to indicate a value is not currently present (although
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// undefined is actually a value itself)
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// `undefined` is actually a value itself)
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// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
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// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
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@ -130,8 +130,9 @@ undefined; // used to indicate a value is not currently present (although
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///////////////////////////////////
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// 2. Variables, Arrays and Objects
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// Variables are declared with the var keyword. JavaScript is dynamically typed,
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// so you don't need to specify type. Assignment uses a single = character.
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// Variables are declared with the `var` keyword. JavaScript is dynamically
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// typed, so you don't need to specify type. Assignment uses a single `=`
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// character.
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var someVar = 5;
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// if you leave the var keyword off, you won't get an error...
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@ -165,7 +166,7 @@ myArray.length; // = 4
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// Add/Modify at specific index
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myArray[3] = "Hello";
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// JavaScript's objects are equivalent to 'dictionaries' or 'maps' in other
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// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
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// languages: an unordered collection of key-value pairs.
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var myObj = {key1: "Hello", key2: "World"};
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@ -190,7 +191,7 @@ myObj.myFourthKey; // = undefined
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// The syntax for this section is almost identical to Java's.
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// The if structure works as you'd expect.
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// The `if` structure works as you'd expect.
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var count = 1;
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if (count == 3){
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// evaluated if count is 3
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@ -200,7 +201,7 @@ if (count == 3){
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// evaluated if it's not either 3 or 4
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}
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// As does while.
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// As does `while`.
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while (true){
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// An infinite loop!
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}
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@ -211,7 +212,7 @@ do {
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input = getInput();
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} while (!isValid(input))
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// the for loop is the same as C and Java:
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// The `for` loop is the same as C and Java:
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// initialisation; continue condition; iteration.
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for (var i = 0; i < 5; i++){
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// will run 5 times
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@ -229,7 +230,7 @@ if (colour == "red" || colour == "blue"){
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var name = otherName || "default";
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// switch statement checks for equality with ===
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// The `switch` statement checks for equality with `===`.
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// use 'break' after each case
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// or the cases after the correct one will be executed too.
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grade = 'B';
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@ -252,14 +253,14 @@ switch (grade) {
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///////////////////////////////////
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// 4. Functions, Scope and Closures
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// JavaScript functions are declared with the function keyword.
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// JavaScript functions are declared with the `function` keyword.
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function myFunction(thing){
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return thing.toUpperCase();
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}
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myFunction("foo"); // = "FOO"
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// Note that the value to be returned must start on the same line as the
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// 'return' keyword, otherwise you'll always return 'undefined' due to
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// `return` keyword, otherwise you'll always return `undefined` due to
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// automatic semicolon insertion. Watch out for this when using Allman style.
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function myFunction()
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{
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@ -298,8 +299,8 @@ i; // = 5 - not undefined as you'd expect in a block-scoped language
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// scope.
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(function(){
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var temporary = 5;
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// We can access the global scope by assiging to the 'global object', which
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// in a web browser is always 'window'. The global object may have a
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// We can access the global scope by assiging to the "global object", which
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// in a web browser is always `window`. The global object may have a
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// different name in non-browser environments such as Node.js.
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window.permanent = 10;
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})();
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@ -312,7 +313,7 @@ permanent; // = 10
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function sayHelloInFiveSeconds(name){
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var prompt = "Hello, " + name + "!";
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// Inner functions are put in the local scope by default, as if they were
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// declared with 'var'.
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// declared with `var`.
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function inner(){
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alert(prompt);
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}
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@ -320,7 +321,7 @@ function sayHelloInFiveSeconds(name){
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// setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
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// exit immediately, and setTimeout will call inner afterwards. However,
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// because inner is "closed over" sayHelloInFiveSeconds, inner still has
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// access to the 'prompt' variable when it is finally called.
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// access to the `prompt` variable when it is finally called.
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}
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sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
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@ -336,7 +337,7 @@ var myObj = {
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myObj.myFunc(); // = "Hello world!"
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// When functions attached to an object are called, they can access the object
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// they're attached to using the this keyword.
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// they're attached to using the `this` keyword.
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myObj = {
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myString: "Hello world!",
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myFunc: function(){
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@ -352,7 +353,7 @@ var myFunc = myObj.myFunc;
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myFunc(); // = undefined
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// Inversely, a function can be assigned to the object and gain access to it
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// through this, even if it wasn't attached when it was defined.
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// through `this`, even if it wasn't attached when it was defined.
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var myOtherFunc = function(){
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return this.myString.toUpperCase();
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}
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@ -360,37 +361,38 @@ myObj.myOtherFunc = myOtherFunc;
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myObj.myOtherFunc(); // = "HELLO WORLD!"
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// We can also specify a context for a function to execute in when we invoke it
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// using 'call' or 'apply'.
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// using `call` or `apply`.
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var anotherFunc = function(s){
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return this.myString + s;
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}
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anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
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// The 'apply' function is nearly identical, but takes an array for an argument list.
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// The `apply` function is nearly identical, but takes an array for an argument
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// list.
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anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
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// This is useful when working with a function that accepts a sequence of arguments
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// and you want to pass an array.
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// This is useful when working with a function that accepts a sequence of
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// arguments and you want to pass an array.
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Math.min(42, 6, 27); // = 6
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Math.min([42, 6, 27]); // = NaN (uh-oh!)
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Math.min.apply(Math, [42, 6, 27]); // = 6
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// But, 'call' and 'apply' are only temporary. When we want it to stick, we can use
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// bind.
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// But, `call` and `apply` are only temporary. When we want it to stick, we can
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// use `bind`.
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var boundFunc = anotherFunc.bind(myObj);
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boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
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// Bind can also be used to partially apply (curry) a function.
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// `bind` can also be used to partially apply (curry) a function.
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var product = function(a, b){ return a * b; }
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var doubler = product.bind(this, 2);
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doubler(8); // = 16
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// When you call a function with the new keyword, a new object is created, and
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// When you call a function with the `new` keyword, a new object is created, and
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// made available to the function via the this keyword. Functions designed to be
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// called like that are called constructors.
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