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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 reall

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 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 14y ago
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 14y ago
In addition I'd say that the interpreter is broken and should be fixed to be faster. "with" is not deprecated.
- slexaxton 14y ago
  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).
- chc 14y ago
  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.

madrobby 14y ago

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 14y ago

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

slexaxton 14y ago
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).
chc 14y ago
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.