The MIME Type text/javascript is used to denote the presence of the JavaScript Source Code file type. This MIME type falls under the text category and must be declared with the TYPE attribute within the SCRIPT element, according to HTML standards. This is considered obsolete by some people because most servers will use the MIME type application/x-javascript to indicate it. The files take the extension JS.

This file type is used to carry the source code for the JavaScript scripting language. JavaScript is used to enable programmatic access to objects within an application. It is primarily used for developing interactive dynamic websites where it is used as client-side JavaScript. It is a dialect of the ECMAScript standard and is described as a weakly typed, prototype-based, dynamic language that has first-class functions. The developers of JavaScript were influenced by many languages while developing it. It is meant to look like Java but is also meant to be easy enough for non-programmers to be able to use it.

It is a language that supports C-type structured programming syntax with the due exception of scoping. The block-level scoping found in C is no supported in JavaScript and is replaced by function-level scoping.