[slexaxton]

Doesn't `with` have significant runtime costs? I didn't think people didn't like that one because it was a 'bad pattern' - I thought it was because it was really slow.

EDIT: I went ahead and JSPerf'd it, and it is 13x slower to run the example in the article.

http://jsperf.com/with-perf

A lot of times this doesn't matter, but it's not nothing.

Edit 2: Also people avoid using `with` so their minification tools have a better chance. Another thing that can be overcome, but just pointing out that it's not religious dogma that makes people avoid `with`.

[madrobby]

I wouldn't use "with" in most situations, but I like it in the testing code and for some DSLs, as it makes things more readable (again, personal style).

I think that once you start optimizing performance problems you need to 1) measure things anyway, and 2) fix on a case-by-case basis. (Don't optimize prematurely, etc.)

[madrobby]

In addition I'd say that the interpreter is broken and should be fixed to be faster. "with" is not deprecated.

[chc]

The trouble with armchair quarterbacking is that many things are easier said than done. It's not like they're deliberately making your code slower — the with-statement makes certain optimizations unfeasible. Their options are to always disable those optimizations or to do it only when there's a with-statement in scope — there's no third option that makes with-statements magically fast. If you can come up with new optimizations that make the with-statement faster, I doubt they'd turn down your patch.

[slexaxton]

I don't believe that this is just an oversight because "people say you shouldn't use `with`". It simply cannot be optimized in the way that normal property accessors are. If you look at old IE perf, they're actually pretty close (both really slow).