More like "write once, run in the browser". I don't think most compile-to-js languages care too much about "anywhere", they are just trying to get nicer alternatives in what is basically a platform (the browser) closed to anything except JS.
It's better than the JVM. It provides an excellent, high-performance runtime for dynamic languages (JS), and an excellent, high-performance runtime for static, memory-unsafe languages (asm.js)!
