Clean up some of the `var`s and loops.

[ljharb]

There's zero reason in 2015 to use a loop, or "var" - this cleans some of them up.

There's still a bunch left, but I figured I'd tackle just a little bit at a time.

[ljharb]

I've updated the diff.

In a JS project, cloning and running npm install should be sufficient to install all dependencies required, and npm test should run any required checks and exit nonzero if any fail. That will also allow you to hook travis-ci up to PRs so that you don't have to manually review many of these kinds of things.