Adding comments. My bad for not adding them first.
Moving player constants into constant variable rather than keeping it in player data.
Adding basic Enemy constructor;

This is basically a copy of the existing _renderEnemies, so it needs
separating properly, which is what i'm doing right now.
Fixing a strange bug caused by firefox not printing out images fast enough. :/
Better utilisation of the constants block.
Improved canvas data output.
Adding new helpers.
Renaming helpr to helpers. Silly shorthand.
Adding new enemy factory and enemy class. Removing old in-built enemy code.
Moving despawn detection to the entity.