Are there legitimate uses for JavaScript's “with” statement?

Question

Alan Storm\'s comments in response to my answer regarding the with statement got me thinking. I\'ve seldom found a reason to use this particular language feature, and had ne

Answer 1

I don't ever use with, don't see a reason to, and don't recommend it.

The problem with with is that it prevents numerous lexical optimizations an ECMAScript implementation can perform. Given the rise of fast JIT-based engines, this issue will probably become even more important in the near future.

It might look like with allows for cleaner constructs (when, say, introducing a new scope instead of a common anonymous function wrapper or replacing verbose aliasing), but it's really not worth it. Besides a decreased performance, there's always a danger of assigning to a property of a wrong object (when property is not found on an object in injected scope) and perhaps erroneously introducing global variables. IIRC, latter issue is the one that motivated Crockford to recommend to avoid with.