##  Specifications

Specification  
---  
[ ECMAScript Language Specification  
#  sec-array.prototype.indexof  ](https://tc39.es/ecma262/multipage/indexed-
collections.html#sec-array.prototype.indexof)  
  
##  Browser compatibility

BCD tables only load in the browser  with JavaScript enabled. Enable
JavaScript to view data.

##  See also

  * [ Polyfill of ` Array.prototype.indexOf ` in ` core-js ` ](https://github.com/zloirock/core-js#ecmascript-array)
  * [ Indexed collections ](/en-US/docs/Web/JavaScript/Guide/Indexed_collections) guide 
  * [ ` Array ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)
  * [ ` Array.prototype.findIndex() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex)
  * [ ` Array.prototype.findLastIndex() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findLastIndex)
  * [ ` Array.prototype.lastIndexOf() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/lastIndexOf)
  * [ ` TypedArray.prototype.indexOf() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/indexOf)
  * [ ` String.prototype.indexOf() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf)

##  Help improve MDN

Was this page helpful to you?

Yes  No

[ Learn how to contribute
](https://github.com/mdn/content/blob/main/CONTRIBUTING.md "This will take you
to our contribution guidelines on GitHub.") .

This page was last modified on  Feb 8, 2024  by  [ MDN contributors ](/en-
US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf/contributors.txt)
.

[ View this page on GitHub
](https://github.com/mdn/content/blob/main/files/en-
us/web/javascript/reference/global_objects/array/indexof/index.md?plain=1
"Folder: en-us/web/javascript/reference/global_objects/array/indexof \(Opens
in a new tab\)") â¢  [ Report a problem with this content
](https://github.com/mdn/content/issues/new?template=page-report.yml&mdn-
url=https%3A%2F%2Fdeveloper.mozilla.org%2Fen-
US%2Fdocs%2FWeb%2FJavaScript%2FReference%2FGlobal_Objects%2FArray%2FindexOf&metadata=%3C%21--+Do+not+make+changes+below+this+line+--%3E%0A%3Cdetails%3E%0A%3Csummary%3EPage+report+details%3C%2Fsummary%3E%0A%0A*+Folder%3A+%60en-
us%2Fweb%2Fjavascript%2Freference%2Fglobal_objects%2Farray%2Findexof%60%0A*+MDN+URL%3A+https%3A%2F%2Fdeveloper.mozilla.org%2Fen-
US%2Fdocs%2FWeb%2FJavaScript%2FReference%2FGlobal_Objects%2FArray%2FindexOf%0A*+GitHub+URL%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fblob%2Fmain%2Ffiles%2Fen-
us%2Fweb%2Fjavascript%2Freference%2Fglobal_objects%2Farray%2Findexof%2Findex.md%0A*+Last+commit%3A+https%3A%2F%2Fgithub.com%2Fmdn%2Fcontent%2Fcommit%2F85d7482697cc2bf407c58e809a2a754180d6714c%0A*+Document+last+modified%3A+2024-02-08T03%3A28%3A22.000Z%0A%0A%3C%2Fdetails%3E
"This will take you to GitHub to file a new issue.")

[ MDN logo  ](/)

Your blueprint for a better internet.

  * [ MDN on Mastodon  ](https://mozilla.social/@mdn)
  * [ MDN on X (formerly Twitter)  ](https://twitter.com/mozdevnet)
  * [ MDN on GitHub  ](https://github.com/mdn/)
  * [ MDN Blog RSS Feed  ](/en-US/blog/rss.xml)

##  MDN

  * [ About ](/en-US/about)
  * [ Blog ](/en-US/blog/)
  * [ Careers ](https://www.mozilla.org/en-US/careers/listings/?team=ProdOps)
  * [ Advertise with us ](/en-US/advertising)

##  Support

  * [ Product help ](https://support.mozilla.org/products/mdn-plus)
  * [ Report an issue ](/en-US/docs/MDN/Community/Issues)

##  Our communities

  * [ MDN Community ](/en-US/community)
  * [ MDN Forum ](https://discourse.mozilla.org/c/mdn/236)
  * [ MDN Chat ](/discord)

##  Developers

  * [ Web Technologies ](/en-US/docs/Web)
  * [ Learn Web Development ](/en-US/docs/Learn)
  * [ MDN Plus ](/en-US/plus)
  * [ Hacks Blog ](https://hacks.mozilla.org/)

[ Mozilla logo  ](https://www.mozilla.org/)

  * [ Website Privacy Notice ](https://www.mozilla.org/privacy/websites/)
  * [ Cookies ](https://www.mozilla.org/privacy/websites/#cookies)
  * [ Legal ](https://www.mozilla.org/about/legal/ter