What is the most efficient way of supporting multiple screen sizes(iphone 4, iphone 5, ipad, ect.) when exporting my game through CocconJs?
With cocoonjs it generally involves methods combined with Scale outer.
There is a lot of in depth information released by scirra on various of these subjects.
This one should get you going in the right direction, Supporting multiple screen sizes by Ashley.
And ofc some general information relating to exporting with cocoonjs
Develop games in your browser. Powerful, performant & highly capable.
This is a good read too... http://gamedevelopment.tutsplus.com/articles/quick-tip-what-is-the-best-screen-resolution-for-your-game--gamedev-14723