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The File Extension Library

What is a file extension?

Short answer: it's the set of letters after the period (.) in the name of a file.

Long answer: File extensions signify the file format of a file. It tells the operating system (OS) how data was stored in the file. Not all OS, require a file extension though. For instance, this is optional in Unix, but is mandatory with MS-DOS and Windows systems.

In most file formats the file type is actually defined by the contents (first bytes, file structure), but extensions are used to define the application that is used for opening the file.

Below is a detailed database of thousands of file extensions our team has compiled for you. Feel free to browse!


Browse all Extensions:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
JS - Extension Details
Date Added: October 09, 2008
File Extension:  .JS
Description 1: .JS file extension is linked with JavaScript file. JavaScript is a language source code file and it a widelyused clientside scripting for internet webpages. JavaScript file on the other hand contains text files that are used to execute the instructions in webpages. Functions may include opening and closing of [webpage] windows, rollover of images, creation of dropdown menus, validation of form fields. JavaScript file is also referenced by webpages which incorporate JavaScript functions. These are usually imported via the HTML's <head> section.
File Type:   Source code and script file
Mode: ASCII
Program(s) to Open:  Windows & Mac: Any web browser, can be edited with a text editor
Common:
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