The JavaScript Programming Language

 JavaScript is a stripped down version of Java
 JavaScript does not exist outside browsers
 JavaScript is inconsistent and buggy
 JavaScript is not object-orientated

 Birth of Mocha, then rename to LiveScript
 Netscape and Sun collaboration for Java in
browsers;
 LiveScript gets renamed to JavaScript
 IE team reverse engineers JavaScript to JScript
 Browser war begins
 Standardization of JavaScript at ECMA;
ECMAScript becomes the official name
 Rise of Ajax
 JavaScript libraries emerge
 ECMAScript 5

 Semicolon insertion
 typeof and instanceof
 with and eval
 == and !=
 new

 Loose Typing
 Dynamic Objects
 Object / Array Literals
 Functions / Lambdas

 Self
 prototypal inheritance
 dynamic objects
 Scheme
 lambda
 loose typing
 Java
 syntax
 conventions
 Perl
 regular expressions

 Numbers
 Strings
 Booleans
 Objects
 Functions

 Number
 String
 Boolean
 Object
 Function
 Array
 Date
 RegExp
 Null
 Undefined

 Only one number type
 No integers
 64-bit floating point IEEE-754 (aka “Double”)
 Numbers are Objects

(a + b) + c === a + (b + c)
Produces false for some values of a, b, c.
Integers under 9007199254740992 (9
quadrillion) are ok.
9007199254740992 === 9007199254740992 + 1

a = 0.1;
b = 0.2;
c = 0.3;
(a + b) + c === a + (b + c)
> false

 Special number: Not a Number
 Result of undefined or erroneous operations
 Toxic: any arithmetic operation with NaN as an
input will have NaN as a result
 NaN is not equal to anything, including NaN
 NaN === NaN is false
 NaN !== NaN is true

 A sequence of 0 or more 16-bit Unicode
characters
 No separate character type
 Characters are represented as strings with length
of 1
 Strings are immutable
 Similar strings are equal ( === )
 String literals can use single or double quotes with
escapement.
 Strings are Objects

> "hello".charAt(0)
h
> "hello, world".replace("hello",
"goodbye")
goodbye, world
> "hello".toUpperCase()
HELLO

 null = deliberately no value
 undefined = no value assigned yet
 Variables declared but not initialized
 Object/array members that don't exist

 Boolean type: true or false
 Everything else is “truthy” or “falsy”
 0, "", NaN, null and undefined are falsy
 Everything else is truthy
 Boolean operations: &&, || and !

 Simple key-value pairs, like:
 HashMaps in Java
 Associative arrays in PHP
 Key is a string; value can be anything
 Key is unique within an object

var obj = new Object();
Or
var obj = {};
These are semantically equivalent; the second is
called object literal syntax and is more
convenient.

obj.name = "My Name"
var name = obj.name;
Or
obj["name"] = "My Name";
var name = obj["name"];
Semantically equivalent; the second uses strings
so can be decided at run-time (and can be
used for reserved words)

var obj = {
name: "Carrot",
"for": "Max",
details: {
color: "orange",
size: 12
}
}
> obj.details.color
Orange
> obj["details"]["size"]
12

Iterate over the keys of an object:
var obj = { 'name': 'Simon', 'age': 25
};
for (var attr in obj) {
alert (attr + ' = ' + obj[attr]);
}
Not to be used with Arrays

 A special type of object: Keys are whole numbers,
not strings.
 Use [] syntax, just like objects
> var a = new Array();
> a[0] = "dog";
> a[1] = "cat";
> a[2] = "hen“;
> a.length
3
 No such thing as “Associative Arrays”

More convenient notation:
> var a = ["dog", "cat", "hen"];
> a.length
3
var a = [10, "dog", false, "elephant"];
(you can have mixed content in arrays)

> var a = ["dog", "cat", "hen"];
> a[100] = "fox";
> a.length
101
typeof a[90] == 'undefined'
array.length is always one more than the
highest index
The safest way to append new items is:
a[a.length] = item;

 New variables are declared using the var
keyword:
 var a;
 var name = "my name";
 If you declare a variable without assigning it to
anything, its value is undefined.
 If you forget the var, you get a global variable.
 Never, ever do this – not even if you mean it.

 Global variables are visible everywhere
 Blocks do not have scope
 Variables defined inside blocks are hoisted to
the top and are visible outside the block
 Functions have scope
 Variables defined inside function are visible
throughout the function and its inner functions

var a;
//...
function F() {
var b;
//...
function N() {
var c;
//...
};
}

 Three different purposes of functions:
 as sub-routine / procedure
 as lambda (a block of executable code)
 as object constructor
 Functions are first-class:
 can be assigned to a variable
 can be passed as argument to any function
 can be returned from any function
 can be a member of any object
 can be created at run time
 Functions can be created inside another function

 Parameters: “They’re more like... Guidelines”
 Missing parameters are treated as undefined:
> add()
NaN // addition on undefined
 You can pass in more arguments than
expected:
> add(2, 3, 4)
5 // added the first two; 4 was ignored

The arguments special variable provides access to arguments as an
array-like object
function add() {
var sum = 0;
for (var i = 0, j = arguments.length; i < j; i++) {
sum += arguments[i];
}
return sum;
}
> add(2, 3, 4, 5)
14

$('#some-id').click(function(evt) {
// do something on click event
};

var add = function(x) {
return function(y) {
return x + y;
};
};

function Person(name) {
this.name = name;
this.getName = function() {
return this.name;
};
}
var person = new Person("some one");
person.getName();
> some one

The JavaScript Programming Language

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The JavaScript Programming Language