Performance impact: sizzle don't use querySelectorAll for specific selector after using $('...').filter('selector') #393

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miflinak opened this Issue Nov 6, 2016 · 0 comments

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@miflinak
miflinak commented Nov 6, 2016 edited

Steps to reproduce

  1. Use filter, for example $('any selector').filter('a, div') (useless but it's just an example).
  2. Call $('a, div') and sizzle wouldn't use querySelectorAll!

That happends because there compilerCache exists for that selector (it was cached when we called filter).

Example: http://jsbin.com/qidopuhiro/1/edit?js,console,output
1 ms vs 15 ms in my case (desktop).

Why that happends?

See https://github.com/jquery/sizzle/blob/abde99f6dc2ed3d489a6d7a52f3df9774be16a32/src/sizzle.js#L295

We can just remove this line. Or do something more complex (like marking cache as filter-only).

You can say "hey, that's just a 15 ms!". But that's much slower on mobile (for example 10 ms vs 150 ms) or when there's many selectors or selectors are complex.
Anyway, why not to use querySelectorAll in cases when we can use it.

@gibson042 gibson042 added a commit to gibson042/sizzle that referenced this issue Nov 21, 2016
@gibson042 gibson042 Selector: Prevent seeded invocations from cutting off the qSA path
Fixes gh-393
3062bff
@gibson042 gibson042 closed this in eabce51 Dec 2, 2016
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