Board Thread:Support Requests - Getting Technical/@comment-25774514-20150210082701/@comment-25428589-20150210085435

There's a list of different places you can add JavaScript here. The options are kinda confusing, so I'll go through them.

If you just want to load JavaScript for yourself, you can use the pages w:Special:MyPage/global.js and Special:MyPage/common.js (although there are others, these are more commonly used). Global.js is stored here on community central and is loaded only for you, but on every wikia you visit. Common.js is stored on a specific wikia, and is loaded only for you, only on that wiki.

If you run a wiki, and want to trigger JavaScript for all users, you can use the pages MediaWiki:Common.js, MediaWiki:Wikia.js and MediaWiki:Monobook.js on the wiki you want to load the JavaScript on (you'll need to be an admin to edit them). Common.js will load for every user, wikia.js will load for users using the default skin and monobook.js will load for users using the monobook skin.

To use these pages, you just create them like you would any other page and use source mode to type in javascript. There are some useful JavaScript codes which work with Wikia at w:c:dev. Best of luck!