Use arrays for children? React.createElement

[syranide]

I thought I'd bring this up before it's set in stone. Since React.createElement is intended mostly as a non-user feature as I understand it, wouldn't it make sense to take the opportunity to also change its signature to React.createElement(type, children) to avoid varargs for a potential perf boost.

Non-scientific test: http://jsperf.com/varargs/2

PS. Hmm, I guess we already support this... by simply providing only an array to children. But it seems that just touching arguments is a significant slow-down (relatively, not necessarily in practice).

cc @sebmarkbage

[plievone]

But it seems that just touching arguments is a significant slow-down (relatively, not necessarily in practice).

There is a good overview of the arguments handling (in V8) here: https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#3-managing-arguments
Surprisingly, using Array.prototype.slice.call(arguments) leaks the arguments object, so it may be better to use an inline arguments slicer helper instead in very hot paths.

[sophiebits]

createElement isn't only an internal API, we use arrays vs. varargs to distinguish child keys, and I believe these have been benchmarked to be comparable (or even faster with varargs?) so I'm going to close this.