"JS" redirects here. See also JScript source file.
JavaScript source file

Filename extension .js +
Internet media type text/javascript
Opens with Web browsers
any text editor
File formats category - v  e   edit
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JavaScript is a scripting language mainly for client-side web development. JavaScript source can be directly embedded inside a web page (HTML or XHTML) or written in an external file.

JavaScript source files, usually ending with .js, are external files that can be linked to from a web page.