Easy Tutorial
Js Scope Jsref Class Extends Js Window Location Js Statements Js Variable Js Typeof Js Lib Prototype Js Cookies Javascript Json Parse Js Strict Js Json Js Conventions Js Loop For Js Function Parameters Js Htmldom Nodelist Js Objects Met Win Postmessage Js Comparisons Js Datatypes Jsref Split Js Ex Objects Js Function Js Chrome Js Async Js Obj String Js Obj Regexp Js Validation Api Js Htmldom Elements Js Form Validation Jsref Obj Array Js Function Closures Jsref Class Super Js Void Js Comments Js Object Prototype Js Ex Browser Js Class Inheritance Js Obj Date Js Summary Js If Else Js Htmldom Html Js Window History Jsref Regexp G Js Syntax Js Obj Math Js Loop While Js Window Jsref Obj Date Js Lib Jquery Js Examples Js Variables Js Switch Js Operators Js Obj Intro Js Break Js Obj Number Jsref Regexp I Js Let Const Js Htmldom Eventlistener Js Obj Array Js Timing Js Errors Jsref Replace Js Mistakes Js Htmldom Js Validation Js Tutorial Js Promise Js Function Invocation Js Reserved Js Htmldom Events Js Ex Dom Jsref Search Js Obj Boolean Js Output Js Libraries Jsref Match Js Htmldom Css Js Regexp Js Type Conversion Js Htmldom Collections Js Function Definition Js Events Js Class Intro Javascript Async Jsref Constructor Class Js Debugging Js Functions Js This Js Window Screen Js Howto Javascript Json Stringify Js Intro Jsref Class Static Js Window Navigator Obj Window Js Class Static Js Strings Index Js Popup Js Hoisting
❮ Js Function Invocation Js Htmldom Events ❯

JavaScript Reserved Keywords

In JavaScript, certain identifiers are reserved keywords and cannot be used as variable names or function names.

JavaScript Standards

All modern browsers fully support ECMAScript 3 (ES3, the third edition of JavaScript, starting from 1999).

ECMAScript 4 (ES4) was not approved.

ECMAScript 5 (ES5, released in 2009).

ECMAScript 6 (ES6, released in 2015), is the latest official version of JavaScript.

Over time, we have seen that all modern browsers now fully support ES6.

JavaScript Reserved Keywords

JavaScript's reserved keywords cannot be used as variables, labels, or function names. Some reserved keywords are reserved for future extensions in JavaScript.

| abstract | arguments | 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 | | |

JavaScript Objects, Properties, and Methods

You should also avoid using the names of JavaScript's built-in objects, properties, and methods as JavaScript variables or function names:

| Array | Date | eval | function | hasOwnProperty | | Infinity | isFinite | isNaN | isPrototypeOf | length | | Math | NaN | name | Number | Object | | prototype | String | toString | undefined | valueOf |

Java Reserved Keywords

JavaScript is often used with Java. You should avoid using some Java objects and properties as JavaScript identifiers:

| getClass | java | JavaArray | javaClass | JavaObject | JavaPackage |

Windows Reserved Keywords

JavaScript can be used outside of HTML. It can be used as a programming language in many other applications.

In HTML, you must (and for portability, you should) avoid using the names of HTML and Windows objects and properties as JavaScript variables and function names:

| 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

Additionally, you should avoid using the names of HTML event handlers as JavaScript variables and function names.

Example:

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

❮ Js Function Invocation Js Htmldom Events ❯