What do you mean? I think you might be missing the point. ECMAScript 3 is almost universally supported to the letter and will continue to be for the forseeable future, just like modern x86 processors are backwards compatible with the ABI from decades ago, and hence is a rock-solid foundation for projects like GWT that compile to it.
ES3 has become the universally compatible "write once, run anywhere" bytecode VM that Java promised to be.
ES3 has become the universally compatible "write once, run anywhere" bytecode VM that Java promised to be.