tree: use more ES6 iterators in the API

[dominicbarnes]

From @dominicbarnes on October 15, 2016 5:57

As I've used ES6 iterators more, I've come to like them more than arrays for their flexibility. (not to mention you can easily use Array.from() if you want an array)

I'm pretty sure this would be a breaking change. (so planned for 2.x)

Copied from original issue: makojs/tree#30

[dominicbarnes]

I'm thinking this would apply to any API that returns a list of File objects, making code that looks like this:

tree.getFiles().forEach(file => {
  // do stuff
})

become more like this:

for (const file of tree.getFiles()) {
  // do stuff
}

[dominicbarnes]

From @darsain on October 15, 2016 8:32

Arrays are already iterable, so the 2nd example is already possible :) In fact, almost everything is iterable. Strings, TypedArrays, function arguments, even those damn NodeLists.

The only thing that you actually need to make iterable are objects. So maybe this:

for (const file of tree) {
  // do stuff
}

[dominicbarnes]

Haha, funny you should bring that up, I started doing that in what I was working on tonight.

Even still, I like to think that I can save on some performance/memory if I'm able to avoid buffering the entire collection with Array.from() before returning, especially since graph.js uses iterators as well.