Javascript files can't find document elements + webgl

New To Meteor. How do I get my javascript files to load after the body of the page? I’m having an issue where if I don’t put the javascript directly into a template, DOM elements used by the scripts can’t be located (all null/undefined).

Also, why can’t I use WebGL inside Meteor? Attempign to use BabylonJS and I get a WEBGL NOT SUPPORTED error…