There is absolutely no reason why this wouldn't be possible in a dynamically typed language. I'm in the process of building such a tool for JS, in fact. You do

There is absolutely no reason why this wouldn't be possible in a dynamically typed language. I'm in the process of building such a tool for JS, in fact. You don't need static typing to do codebase-wide renaming, it just makes it a little easier to build the refactoring tools, but since that is a one-time cost it's not really a particularly important factor in the language design. Other language design decisions have much more influence on this development cost, too, such as reassignability and scoping rules. "Strong typing" is also something totally different from "static typing" - I'm not sure why you're bringing it up here. The two are not interchangeable terms. EDIT: Actually, doesn't Webstorm already do such mass-renaming for JS? EDIT 2: I also object to the use of the word 'refactoring' to refer exclusively to renaming variables. Proper refactoring involves much more work, most of which isn't automatable regardless of the language you're using.