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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 Data Types JS Functions JS Objects JS Events JS Strings JS String Methods JS String Search JS Numbers JS Number Methods JS Arrays JS Array Methods JS Array Sort JS Array Iteration JS Array Const JS Dates JS Date Formats JS Date Get Methods JS Date Set Methods JS Math JS Random JS Booleans JS Comparisons JS Conditions JS Switch JS Loop For JS Loop For In JS Loop For Of JS Loop While JS Break JS Typeof JS Type Conversion JS Bitwise JS RegExp JS Errors JS Scope JS Hoisting JS Strict Mode JS this Keyword JS Arrow Function JS Classes JS JSON JS Debugging JS Style Guide JS Best Practices JS Mistakes JS Performance JS Reserved Words

JS Objects

Object Definitions Object Properties Object Methods Object Display Object Accessors Object Constructors Object Prototypes Object Reference Object Map() Object Set()

JS Functions

Function Definitions Function Parameters Function Invocation Function Call Function Apply Function Closures

JS Classes

Class Intro Class Inheritance Class Static

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 IE / Edge JS History

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 Forms 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 Examples

JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Editor

JS References

JavaScript Objects HTML DOM Objects


JavaScript Reserved Words

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In JavaScript you cannot use these reserved words as variables, labels, or function names:
abstract arguments 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 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 var void
volatile while with yield
Words marked with* are new in ECMAScript 5 and 6.

You can read more about the different JavaScript versions in the chapter JS Versions.

Removed Reserved Words

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

Do not use these words as variables. ECMAScript 5/6 does not have full support in all browsers.

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

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