Migrate away from using `this` - quick fix WIP (NOT TESTED)

[brody4hire]

Wanted to make the code even more pure.

Input ref updated as described in: https://gist.github.com/gaearon/1a018a023347fe1c2476073330cc5509 (linked from https://reactjs.org/docs/refs-and-the-dom.html)

TODO:

• needs testing
• change let self to const self and do return self at the end of the function