About this Reference

The JavaScript Reference serves as a repository of facts about the JavaScript language. The entire language is described here in detail. As you write JavaScript code, you'll refer to these pages often (thus the title "JavaScript Reference"). If you're learning JavaScript, or need help understanding some of its capabilities or features, check out the JavaScript Guide

What you should already know

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) {
  console.log(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

JavaScript (SpiderMonkey) version Mozilla release Gecko version
JavaScript 1.5 Navigator 6.0, Mozilla Application Suite, Firefox 1.0 Gecko 0.6x-1.7
JavaScript 1.6 Firefox 1.5 Gecko 1.8
JavaScript 1.7 Firefox 2 Gecko 1.8.1
JavaScript 1.8 Firefox 3 Gecko 1.9
JavaScript 1.8.5 Firefox 4 Gecko 2.0
JavaScript 1.8.6 Firefox 17 Gecko 17

Where to find JavaScript information

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

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.

Document Tags and Contributors

Last updated by: dbruant,