Edits to section on strings and numbers

This commit is contained in:
Adam Brenecki 2013-06-30 17:44:25 +09:30
parent 600b5b5b74
commit 7c4bd7120c

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@ -26,29 +26,34 @@ doStuff();
// wherever there's a newline, except in certain cases. // wherever there's a newline, except in certain cases.
doStuff() doStuff()
// Semicolons are a heated topic in the JavaScript world, but they're really a // We'll leave semicolons off here; whether you do or not will depend on your
// matter of personal or style-guide preference. We'll leave them off here. // personal preference or your project's style guide.
/*********** /***********
* 1. Primitive Datatypes and Operators * 1. Numbers, Strings and Operators
***********/ ***********/
// Javascript has one number type that covers ints and floats. // Javascript has one number type that covers ints and floats.
3 // = 3 3 // = 3
1.5 // = 1.5 1.5 // = 1.5
// which support all the operations you'd expect. // All the basic arithmetic works as you'd expect.
1 + 1 // = 2 1 + 1 // = 2
8 - 1 // = 7 8 - 1 // = 7
10 * 2 // = 20 10 * 2 // = 20
35 / 5 // = 7 35 / 5 // = 7
// Uneven division works how you'd expect, too. // Including uneven division.
5 / 2 // = 2.5 5 / 2 // = 2.5
// Enforce precedence with parentheses // Enforce precedence with parentheses
(1 + 3) * 2 // = 8 (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
// There's also a boolean type. // There's also a boolean type.
true true
false false
@ -70,10 +75,10 @@ false
2 != 1 // = true 2 != 1 // = true
// More comparisons // More comparisons
1 < 10 // => True 1 < 10 // = true
1 > 10 // => False 1 > 10 // = false
2 <= 2 // => True 2 <= 2 // = true
2 >= 2 // => True 2 >= 2 // = true
// Strings are concatenated with + // Strings are concatenated with +
"Hello " + "world!" // = "Hello world!" "Hello " + "world!" // = "Hello world!"
@ -81,17 +86,21 @@ false
// and are compared with < and > // and are compared with < and >
"a" < "b" // = true "a" < "b" // = true
// You can also compare strings with numbers // Type coercion is performed for comparisons...
"5" == 5 // = true "5" == 5 // = true
// but this is almost always not what you want, so use === to stop this // ...unless you use ===
"5" === 5 // = false "5" === 5 // = false
// You can access characters in a string with charAt // You can access characters in a string with charAt
"This is a string".charAt(0) "This is a string".charAt(0)
// There's also a null keyword // There's also null and undefined
null // = null null // used to indicate a deliberate non-value
undefined // used to indicate a value that hasn't been set yet
// null, undefined, NaN, 0 and "" are falsy, and 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