Refactor JS code to meet a consistent standard

[jacksonconte]

Formatting inconsistencies include but are not limited to:

• [ ] Use of const vs let
• [ ] Use of double quotes vs single quotes in JS
• [ ] Use of arrow functions vs function() {...
• [ ] Indentation: 2 spaces vs 4 spaces
• [ ] For-each loops: for... of vs forEach()

We need a list of style rules somewhere as a source of truth #10