> Why don't browsers support a sand-boxed python (or insert favorite language x) with some sort of standard dependency management? It already has JIT compilatio

> Why don't browsers support a sand-boxed python (or insert favorite language x) with some sort of standard dependency management? It already has JIT compilation, is cross-platform, bytecode, a wealth of libraries, etc. Why are we reinventing this wheel? 1. Python is not sandboxed. Security is necessary in a web browser. 2. Python has some JIT work, mainly PyPy, but even so is much slower than JavaScript. 3. You can compile Python into JavaScript (see demo at repl.it), where it will be sandboxed. Similar reasons apply to other proposed languages, for a web language we need security, speed, standardization, and portability (and often we can already compile them into JS, so the motivation is lessened anyhow). I am unaware of any option that has all of those to the extent that JavaScript does.