JavaScript Reference

About this Reference

Some programming experience with a language such as C or Visual Basic is useful, but not required.

The JavaScript language is intended to be used within some larger environment, be it a browser, server-side scripts, or similar. For the most part, this reference attempts to be environment-agnostic and does not target a web browser environment. For demonstration purposes, this reference uses a function, println, which is not part of JavaScript and can be mapped to environment-specific functionality to display given values. For example, in a web browser println might have been defined as follows:

function println(string) {
  window.alert(string);
}

Mapping to equivalent functionality in other environments is left as an exercise for the reader.

Formatting conventions

This reference includes descriptive syntax sections to demonstrate appropriate or common usage of the subject of documentation. Within these sections, all text literals to be reproduced verbatim are non-italicized, with the exception of ellipses. Words in italics represent user-defined names or statements. Any portions enclosed in square brackets ([ and ]) are optional. A comma-delimited sequence that includes an ellipsis (...) indicates that the sequence is a list and all items in the sequence except the first are optional (e.g. only param1 is required in "param1, param2, ..., paramN").

JavaScript history

Recent versions of Mozilla-based browsers support newer versions of JavaScript. The following table lists the JavaScript version supported by different Mozilla-based browser versions.

Browsers that do not support at least JavaScript 1.5 are very rare today, since JavaScript 1.5 was introduced back in 1999. If you're interested in historic information, please refer to the Wikipedia article on ECMAScript.

JavaScript/Browser support history

Where to find JavaScript information

JavaScript documentation of core language features (pure ECMAScript, for the most part) includes the following:

• The JavaScript Guide
• The JavaScript Reference

If you are new to JavaScript, start with the Guide. Once you have a firm grasp of the fundamentals, you can use the Reference to get more details on individual objects and language constructs.

Global Objects

General-purpose constructors

• Array
• Boolean
• Date
• Function
• Iterator
• Number
• Object
• RegExp
• String

Typed array constructors

• ArrayBuffer
• DataView
• Float32Array
• Float64Array
• Int16Array
• Int32Array
• Int8Array
• Uint16Array
• Uint32Array
• Uint8Array
• Uint8ClampedArray

Error constructors

• Error
• EvalError
• InternalError
• RangeError
• ReferenceError
• StopIteration
• SyntaxError
• TypeError
• URIError

Non-constructor functions

• decodeURI
• decodeURIComponent
• encodeURI
• encodeURIComponent
• eval
• isFinite
• isNaN
• parseFloat
• parseInt
• uneval

Other

• Infinity
• JSON
• Math
• NaN
• undefined

Functions and function scope

• arguments
• Strict mode

Statements

JavaScript statements consist of keywords used with the appropriate syntax. A single statement may span multiple lines. Multiple statements may occur on a single line if each statement is separated by a semicolon.

• break
• continue
• debugger
• do...while
• for...in
• function
• if...else
• return
• switch
• throw
• try...catch
• var
• while
• with

Operators and other keywords

There are several special operators that do not fit into any other category:

Arithmetic Operators

(+, -, *, /, %, ++, --, unary -, unary +)

Arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value.

Assignment Operators

(=, *=, /=, %=, +=, -=, <<=, >>=, >>>=, &=, ^=, |=)

An assignment operator assigns a value to its left operand based on the value of its right operand.

Bitwise Operators

(&, |, ^, ~, <<, >>, >>>)

Bitwise operators treat their operands as a set of 32 bits (zeros and ones) and return standard JavaScript numerical values.

Comparison Operators

(==, !=, ===, !==, >, >=, <, <=)

A comparison operator compares its operands and returns a logical value based on whether the comparison is true.

Logical Operators

(&&, ||, !)

Logical operators are typically used with boolean (logical) values, and when they are, they return a boolean value.

String Operators

(+ and +=)

The string operators concatenate two string values together, returning another string that is the union of the two strings.

Member Operators

(object.property and object["property"])

Member operators provide access to a property or method of an object.

Special Operators

Conditional Operator

(condition ? ifTrue : ifFalse)

The conditional operator returns one of two values based on the logical value of the condition.

Comma Operator

(,)

The comma operator allows multiple expressions to be evaluated in a single statement and returns the result of the last expression.

delete Operator

(delete)

The delete operator deletes objects.

function Operator

(function)

The function operator defines a function.

get Operator

(get)

The get operator defines a property to be a getter.

in Operator

(in)

The in operator determines whether an object has a given property.

instanceof Operator

(instanceof)

The instanceof operator determines whether an object is an instance of another object.

let Operator

(let)

The let operator temporarily assigns a value to a variable that only effects an expression.

new Operator

(new)

The new operator creates an instance of a constructor.

set Operator

(set)

The set operator defines a property to be a setter.

this Operator

(this)

The this operator refers to the execution context.

typeof Operator

(typeof)

The typeof operator determines the type of a given object.

void Operator

(void)

The void operator discards an expressions return value.

yield Operator

(yield)

The yield operator determines what is returned in a generator by that generator's iterator.

Operator Precedence

Operator precedence defines the order in which operators are evaluated.

Comments

• Code comments (// and /* */)

E4X (extension)Deprecated

Global statements:

• default XML namespace

Global functions:

• isXMLName()

Global constructors:

• Namespace()
• QName()
• XML()
• XMLList()

Appendix A - Reserved Words

Appendix B - Deprecated Features

Original Document At: http://devedge-temp.mozilla.org/libr...1.5/reference/