Tern & Threejs support
tern-threejs provides the threejs tern plugin which gives you a support for three.js.
After installing and converting your project as Tern Project (see Tern-Eclipse-IDE), open Project Properties, click on Tern / Modules item and select the three.js tern plugin (ECMAScript 6 and Browser tern plugin must be selected too) :
After that you can benefit with three.js completion :
You can play with online demo which uses CodeMirror (inside Web Browser).