In fairness Visual Studio (and most IDEs) are pretty bloated and slow.
As to the grandparent, that is what asm.js was for, was a subset of JS that could be heavily optimized and JITed... I also really prefer .Net method of native invocation over JNI stubs.
After several years of working with VS, Eclipse, and a couple of other developers' IDEs, I can say -with a straight face- that developers' IDEs are slow primarily because they do a lot of work.
Absolutely.. and if you're using one on a system without an SSD, it's outright painful. There's a lot that goes on with IDEs, effectively on-demand compilation, file watching, and there's a lot to that.
Of course, sometimes I find I'm actually more effected when I can just work on a small module in a plain text editor, and keep things organized so its' relatively easy to follow.
As to the grandparent, that is what asm.js was for, was a subset of JS that could be heavily optimized and JITed... I also really prefer .Net method of native invocation over JNI stubs.