Smart! But will it work without actually running the code? Will you be sure that the method which is available on the object now is available on each object passed to the method you're writing?

Visual Studio autocompletes Javascript by executing the Javascript and using stub objects for anything that they don't actually want to run (e.g. window, XmlHttpRequest, etc).

That sounds incredibly baroque, complicated, and fragile.

Sure it is, but so what? Would statically analyzing the code really get you any further?

Type inference would get you quite a way. Using a language that allows effective tooling would get you even farther.

Replacing Javascript with a better language has not been possible thus far. There have been many attempts, but getting every browser maker to agree on something is like herding cats.

So, when life gives you lemons, you make lemonade. We're stuck with Javascript. Personally, I think running the code while you're developing it is a brilliant way of dealing with the problem of how to do proper autocomplete on a dynamic language.

.. in other words, javascript

That kind of auto completion is very easy to do. The problem is when you have references whose creation site you can't trace statically.

To be fair, it's also probably a 90/10 situation. And whether or not it's easy to do, it's somewhat rare to see in the tools that most people use for non-static languages.

Even in Java and C#, arguably the best languages re: deep IDE integration, there are edge cases where the IDE can't know everything (reflection, for instance), but it still does the trick most of the time.