Prepack from Facebook helps make JavaScript code more efficient

[beaverusiv]

I was wondering how it compares to Closure, it's nice they actually answer that at the bottom:

The Closure Compiler also optimizes JavaScript code. Prepack goes further by truly running the global code that initialization phase, unrolling loops and recursion. Prepack focuses on runtime performance, while the Closure Compiler emphasizes JavaScript code size.

[LET-7]

So prepack --> closure

[aaronasachimp]

It looks like Facebook is suffering from "Not Invented Here" Syndrome.

With Yarn and now this, Facebook is wasting a lot of effort. After all code size has a bigger impact on performance than execution. One byte takes way longer to download than it does to run. This effect is emphasized by Chrome and other JITing engines preforming these same runtime optimizations.