> It is, but you can also port existing applications to JS.
You can't just port things to JavaScript the same way. JavaScript is a very different sort of language. "porting" something to JavaScript pretty much always means remaking the whole thing from ground up and hoping that your pixel pushing in canvas runs at an acceptable speed.
It's not orders of magnitude slower, most benchmarks have it 2x-6x slower. It's rarely slower than 10x (one order of magnitude). And that is before JS engines even start to optimize for it.
You can't just port things to JavaScript the same way. JavaScript is a very different sort of language. "porting" something to JavaScript pretty much always means remaking the whole thing from ground up and hoping that your pixel pushing in canvas runs at an acceptable speed.