replace bind()

[mscdex]

This is anticipation of Writable changes landing in nodejs/node#6533

/cc @calvinmetcalf @mcollina

[mcollina]

Amazing, thanks!
LGTM

[calvinmetcalf]

ok this works fine because we put it through babel to deal with the arrow functions, but I wonder why node core couldn't use the arrow function?

[mcollina]

bind() changed from being a v8 killer to be faster than arrow functions from node v7+.

[mscdex]

@mcollina s/arrow functions/inline closures/

[mcollina]

@mscdex yes sorry. bind() is now faster than using function to wrap this.

[calvinmetcalf]

so readable stream is intended for use in all versions of node/multiple browsers so I'm not sure the wisdom of including optimizations for older platforms, chrome for instance will be negatively effected by this

[mscdex]

@calvinmetcalf Well, it's not just older node versions but also possibly other javascript engines that might not optimize the same things. I personally do not see a straight-forward solution because readable-stream is/could be used in so many different environments. If we leave the bind() it might work better in some environments but worse in others, same goes for reverting its usage. The same also goes for #255.

I just created these PRs because @mcollina had mentioned in the upstream node PR that he considered performance changes to be breaking.

[mcollina]

@calvinmetcalf using bind() in node v0.10/v0.12 and the like can cause a massive slowdown. See Level/levelup#139 as an example. If we want to play it safe, we should really benchmark this change on node v0.10-v6, and see if it impacts things. Or, we can do the change and avoid potential breakage (yes, I consider a major slowdown a breakage).

[mcollina]

We are going to merge this on the next update, as decided in #252

[mcollina]

Part of #262