History

	LiveScript Designed by Brendan Eich
	1995 - Shipped in Netscape Navigator 2.0
	1996 - JScript at Microsoft
	1998 - ECMAScript

Key Ideas

• Load and go delivery
• Dynamic typing
• Objects as general containers
• Prototypal inheritance
• First class functions (Lambdas)
• Linkage through global variables

Values

• Numbers (64-bit floating point)
• Strings (0 or more 16bit characters)
• Booleans (true or false)
• Objects (Associative arrays, augmented with prototypes)
• Arrays
• null (a value that is nothing)
• undefined (default value of members)
• NaN (Not a number)

Number

Math

Strings

Booleans

null and undefined

Date

Falsy values

Objects

Arrays

• Array indices: If a key is a string holding a non-negative integer below a certain maximum then it is treated as an array index.
• "length": The value of this property is a non-negative integer holding the length of an array. That length is defined as the numerically largest array index, converted to integer, plus one

Arrays

Is Array?

Dynamic Typing

Reserved words

abstract else instanceof super boolean enum int switch break export interface synchronized byte extends let this case false long throw catch final native throws char finally new transient class float null true const for package try continue function private typeof debugger goto protected var default if public void delete implements return volatile do import short while double in static with

Operators

• Arithmetic ( + - * / % )
• Logical ( && || ! )
• Ternary ( ?: )
• Comparison ( == != > < >= <= === !== )

+ /

== !=

=== !==

&& (guard operator)

|| (default operator)

Statements

• expression
• if
• for/do/while
• break/continue
• switch
• return
• try/throw

break

for

switch

try/catch

with

function

Scope

Objects

• Set of unordered key/value pairs
• Keys (names) are strings
• Values can be objects, functions, numbers, etc
• Objects can inherit from other objects (no classes)

Objects

Object linking

Object linking (the right way part 1)

Object linking (the right way part 2)

Classical inheritance

JSON - JavaScript Object Notation

Global Object

• Container for global variables
• 'window' in the browser, 'global' in nodejs
• Use of global variables can cause collisions
• Variables not properly declared can become global

Encapsulation

eval

RegExp

toString()

Threads

Always put { on the right

,

Common scope error

Strict mode

Asynchronous Module Definition

Debugging

• debugger; can be added to represent a breakpoint
• console.log/warn/error can be used for logging
• F12 will open the Dev Tools in most browsers
• Use Chrome!
• Use Firebug in Firefox
• Write unit tests - QUnit

Key Ideas

• Load and go delivery
• Dynamic typing
• Objects as general containers
• Prototypal inheritance
• First class functions (Lambdas)
• Linkage through global variables

Credits

• Inspired by Douglas Crockford's javascript lectures