Menu
×
Get Certified Upgrade For Teachers Spaces Get Certified Upgrade For Teachers Spaces
   ❮     
HTML CSS JAVASCRIPT SQL PYTHON JAVA PHP HOW TO W3.CSS C C++ C# BOOTSTRAP REACT MYSQL JQUERY EXCEL XML DJANGO NUMPY PANDAS NODEJS DSA TYPESCRIPT ANGULAR GIT POSTGRESQL MONGODB ASP AI R GO KOTLIN SASS VUE GEN AI SCIPY CYBERSECURITY DATA SCIENCE INTRO TO PROGRAMMING BASH RUST

JS Tutorial

JS HOME JS Introduction JS Where To JS Output JS Statements JS Syntax JS Comments JS Variables JS Let JS Const JS Operators JS Arithmetic JS Assignment JS Functions JS Objects JS Events JS Strings JS String Templates JS Numbers JS Arrays JS Dates JS Math JS Random JS Booleans JS Comparisons JS If Else JS Switch JS Loops JS Break JS Continue JS Errors JS Modules JS News 2025-2015

JS Statements

JS Statements JS Keywords Reference JS Keywords Reserved JS Operator Reference JS Operator Precedence

JS Data Types

JS Data Types JS typeof JS toString() JS Type Conversion

JS Strings

JS String Methods JS String Search JS String Reference

JS Numbers

JS Number Methods JS Number Properties JS Number Reference JS Math Reference JS BigInt JS Bitwise

JS Dates

JS Date Formats JS Date Get JS Date Set JS Date Reference

JS Arrays

JS Array Methods JS Array Search JS Array Sort JS Array Iterations JS Array Reference JS Array Const

JS Functions

Function Definitions Function Arrows Function Parameters Function Invocation Function this Function Call Function Apply Function Bind Function Closures

JS Objects

Object Definitions Object Properties Object Methods Object Display Object Constructors Object this Object Destructuring Object Prototypes Object Iterations Object Management Object Get / Set Object Protection Object Reference

JS Classes

JS Classes JS Class Inheritance JS Class Static

JS Sets & Maps

JS Sets JS Set Methods JS Set Logic JS Set Reference JS Maps JS Map Methods JS Map Reference

JS Typed Arrays

JS Typed Arrays JS Typed Methods JS Typed Reference

JS Iterations

JS Loop For JS Loop While JS Loop For In JS Loop For Of JS Iterables JS Iterators

JS RegExp

JS RegExp JS RegExp Flags JS RegExp Classes JS RegExp Metachars JS RegExp Assertions JS RegExp Quantifiers JS RegExp Patterns JS RegExp Objects JS RegExp Methods

JS Async

JS Callbacks JS Asynchronous JS Promises JS Async/Await

JS Versions

JS Versions JS 2009 (ES5) JS 2015 (ES6) JS 2016 JS 2017 JS 2018 JS 2019 JS 2020 JS 2021 JS 2022 JS 2023 JS 2024 JS 2025 JS IE / Edge JS History

JS Programming

JS Strict Mode JS Scope JS Hoisting JS Debugging JS Style Guide JS Best Practices JS Mistakes JS Performance

JS HTML DOM

DOM Intro DOM Methods DOM Document DOM Elements DOM HTML DOM Forms DOM CSS DOM Animations DOM Events DOM Event Listener DOM Navigation DOM Nodes DOM Collections DOM Node Lists

JS Browser BOM

JS Window JS Screen JS Location JS History JS Navigator JS Popup Alert JS Timing JS Cookies

JS Web APIs

Web API Intro Web Validation API Web History API Web Storage API Web Worker API Web Fetch API Web Geolocation API

JS AJAX

AJAX Intro AJAX XMLHttp AJAX Request AJAX Response AJAX XML File AJAX PHP AJAX ASP AJAX Database AJAX Applications AJAX Examples

JS JSON

JSON Intro JSON Syntax JSON vs XML JSON Data Types JSON Parse JSON Stringify JSON Objects JSON Arrays JSON Server JSON PHP JSON HTML JSON JSONP

JS vs jQuery

jQuery Selectors jQuery HTML jQuery CSS jQuery DOM

JS Graphics

JS Graphics JS Canvas JS Plotly JS Chart.js JS Google Chart JS D3.js

JS Examples

JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Editor JS Exercises JS Quiz JS Website JS Syllabus JS Study Plan JS Interview Prep JS Bootcamp JS Certificate

JS References

JavaScript Objects HTML DOM Objects


JavaScript Reserved Words

❮ Previous Next ❯
In JavaScript you cannot use these reserved words as variables, labels, or function names:
abstract arguments async * await *
boolean break byte case
catch char class * const *
continue debugger default delete
do double else enum *
eval export * extends * false
final finally float for
function goto if implements
function import * in instanceof
int interface let * long
native new null package
private protected public return
short static super * switch
synchronized this throw throws
transient true try typeof
using * var void volatile
while with yield

Note

Words marked with* have been added to JavaScript from after 2015.

You can read more the newest JavaScript versions in JS News 2025-2015.

Removed Reserved Words

The following reserved words was removed from the ECMAScript 5/6 standard:
abstract boolean byte char
double final float goto
int long native short
synchronized throws transient volatile

JavaScript Objects, Properties, and Methods

You should also avoid using the name of JavaScript built-in objects, properties, and methods:
Array Date eval function
hasOwnProperty Infinity isFinite isNaN
isPrototypeOf length Math NaN
name Number Object prototype
String toString undefined valueOf

Java Reserved Words

JavaScript is often used together with Java. You should avoid using some Java objects and properties as JavaScript identifiers:
getClass java JavaArray javaClass
JavaObject JavaPackage

Other Reserved Words

JavaScript can be used as the programming language in many applications.

You should also avoid using the name of HTML and Window objects and properties:
alert all anchor anchors
area assign blur button
checkbox clearInterval clearTimeout clientInformation
close closed confirm constructor
crypto decodeURI decodeURIComponent defaultStatus
document element elements embed
embeds encodeURI encodeURIComponent escape
event fileUpload focus form
forms frame innerHeight innerWidth
layer layers link location
mimeTypes navigate navigator frames
frameRate hidden history image
images offscreenBuffering open opener
option outerHeight outerWidth packages
pageXOffset pageYOffset parent parseFloat
parseInt password pkcs11 plugin
prompt propertyIsEnum radio reset
screenX screenY scroll secure
select self setInterval setTimeout
status submit taint text
textarea top unescape untaint
window

HTML Event Handlers

In addition you should avoid using the name of all HTML event handlers.

Examples:
onblur onclick onerror onfocus
onkeydown onkeypress onkeyup onmouseover
onload onmouseup onmousedown onsubmit

❮ Previous Next ❯
PLUS
SPACES
GET CERTIFIED
FOR TEACHERS
FOR BUSINESS
CONTACT US
×

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail:
sales@w3schools.com

Report Error

If you want to report an error, or if you want to make a suggestion, send us an e-mail:
help@w3schools.com

Top Tutorials
HTML Tutorial
CSS Tutorial
JavaScript Tutorial
How To Tutorial
SQL Tutorial
Python Tutorial
W3.CSS Tutorial
Bootstrap Tutorial
PHP Tutorial
Java Tutorial
C++ Tutorial
jQuery Tutorial
Top References
HTML Reference
CSS Reference
JavaScript Reference
SQL Reference
Python Reference
W3.CSS Reference
Bootstrap Reference
PHP Reference
HTML Colors
Java Reference
Angular Reference
jQuery Reference
Top Examples
HTML Examples
CSS Examples
JavaScript Examples
How To Examples
SQL Examples
Python Examples
W3.CSS Examples
Bootstrap Examples
PHP Examples
Java Examples
XML Examples
jQuery Examples
Get Certified
 HTML Certificate
CSS Certificate
JavaScript Certificate
Front End Certificate
SQL Certificate
Python Certificate
PHP Certificate
jQuery Certificate
Java Certificate
C++ Certificate
C# Certificate
XML Certificate
FORUM ABOUT ACADEMY
W3Schools is optimized for learning and training. Examples might be simplified to improve reading and learning.
Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness
of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.

Copyright 1999-2025 by Refsnes Data. All Rights Reserved. W3Schools is Powered by W3.CSS.