
Array Concat vs. Spread - laex
https://jsperf.com/array-concat-vs-spread
======
Asraelite
I've always found it somewhat confusing how common operations like this with
identical behavior but differing syntax can have such drastic differences in
speed. Another example would be `for (let i in array) { array[i]...` versus
`array.forEach(...`.

For highly optimized engines like V8 and SpiderMonkey, it seems like
recognizing these cases and automatically substituting in the faster behavior
would be pretty low hanging fruit that could have a significant impact on
existing scripts' performance.

Maybe there's some underlying reason to do with how these engines work
internally that prevents such optimizations from easily being performed
though.

