JavaScript (JS) is a lightweight interpreted or JIT-compiled programming language with first-class functions. While it is most well-known as the scripting language for Web pages, many non-browser environments also use it, such as node.js, Apache CouchDB and Adobe Acrobat. JavaScript is a prototype-based, multi-paradigm, dynamic language, supporting object-oriented, imperative, and declarative (e.g. functional programming) styles. Read more about JavaScript.

This section of the site is dedicated to the JavaScript language itself, and not the parts that are specific to Web pages or other host environments. For information about APIs specific to Web pages, please see Web APIs and DOM.

The standard for JavaScript is ECMAScript. As of 2012, all modern browsers fully support ECMAScript 5.1. Older browsers support at least ECMAScript 3. On June 17, 2015, ECMA International published the sixth major version of ECMAScript, which is officially called ECMAScript 2015, and was initially referred to as ECMAScript 6 or ES6. Since then, ECMAScript standards are on yearly release cycles. This documentation refers to the latest draft version, which is currently ECMAScript 2018.

Do not confuse JavaScript with the Java programming language. Both "Java" and "JavaScript" are trademarks or registered trademarks of Oracle in the U.S. and other countries. However, the two programming languages have very different syntax, semantics, and uses.


Learn how to program in JavaScript with guides and tutorials.

For complete beginners

Head over to our Learning Area JavaScript topic if you want to learn JavaScript but have no previous experience of JavaScript or programming. The complete modules available there are as follows:

JavaScript first steps
Answers some fundamental questions such as "what is JavaScript?", "what does it look like?", and "what can it do?", along with discussing key JavaScript features such as variables, strings, numbers and arrays.
JavaScript building blocks
Continues our coverage of JavaScript's key fundamental features, turning our attention to commonly-encountered types of code block such as conditional statements, loops, functions, and events.
Introducing JavaScript objects
The object-oriented nature of JavaScript is important to understand if you want to go further with your knowledge of the language and write more efficient code, therefore we've provided this module to help you.

JavaScript guide

JavaScript Guide
A much more detailed guide to the JavaScript language, aimed at those with previous programming experience either in JavaScript or another language.


A re-introduction to JavaScript
An overview for those who think they know about JavaScript.
JavaScript data structures
Overview of available data structures in JavaScript.
Equality comparisons and sameness
JavaScript provides three different value-comparison operations: strict equality using ===, loose equality using ==, and the method.


Inheritance and the prototype chain
Explanation of the widely misunderstood and under-estimated prototype-based inheritance.
Strict mode
Strict mode defines that you can not use any variable before initializing it. It is a restricted variant of ECMAScript 5, for faster performance and easier debugging.
JavaScript typed arrays
JavaScript typed arrays provide a mechanism for accessing raw binary data.
Memory Management
Memory life cycle and garbage collection in JavaScript.
Concurrency model and Event Loop
JavaScript has a concurrency model based on an "event loop".


Browse the complete JavaScript reference documentation.

Standard objects
Get to know standard built-in objects Array, Boolean, Date, Error, Function, JSON, Math, Number, Object, RegExp, String, Map, Set, WeakMap, WeakSet, and others.
Expressions and operators
Learn more about the behavior of JavaScript's operators instanceof, typeof, new, this, the operator precedence, and more.
Statements and declarations
Learn how do-while, for-in, for-of, try-catch, let, var, const, if-else, switch, and more JavaScript statements and keywords work.
Learn how to work with JavaScript's functions to develop your applications.

Tools & resources

Helpful tools for writing and debugging your JavaScript code.

Firefox Developer Tools
Scratchpad, Web Console, JavaScript Profiler, Debugger, and more.
JavaScript Shells
A JavaScript shell allows you to quickly test snippets of JavaScript code.
Collaboration made easy. By adding TogetherJS to your site, your users can help each other out on a website in real time!
Stack Overflow
Stack Overflow questions tagged with "JavaScript".
JavaScript versions and release notes
Browse JavaScript's feature history and implementation status.
Edit JavaScript, CSS, HTML and get live results. Use external resources and collaborate with your team online.

Join the JavaScript community

Choose your preferred method for joining the discussion:

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