[thermodynthrway]

Transpiled JS specifically. JS is the only popular language with a great deal of differences between versions and runtimes, mostly due to rapid improvements. If you use "vanilla" ES2017 without transpilation you're in for a deluge of bug reports.

Instead of worrying about browser Y supporting feature X, I just ram everything through Babel or Typescript compilers and use all the newest features.

We haven't had a single browser specific JS bug since we started using Typescript on ny project last year. And async is so damn nice.

Babel's output is a bit obtuse sometimes, but Typescript was designed to output idiomatic JS, so even with no sourcemaps code is perfectly readable before minification