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Re: filter queryselectorall

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Michael Haufe (TNO) wrote:

> More like a pin-hammer. This is a general solution to the problem of
> manipulating NodeLists, not solving this particular problem. The
> alternative formulation, to avoid a potential compilation step for
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
How so?

> down-rev environments would be:
> 
> function qsa(s,ctx){return
> [].slice.call((ctx||document).querySelectorAll(s))}
> 
> But is a more low-level[1] solution.
> 
>> Instead:
>> 
>>   var clickables = [].filter.call(
>>     document.querySelectorAll('[id^="clickable_"]'),
>>     function (element) { return /_\d+$/.test(element.id); });
> 
> Using the form above:
> 
> var clickables = qsa('[id^="clickable_"]').filter(e => /_\d+$/.test(e.id))

Yes, but one problem with converting a NodeList into an Array is that 
NodeLists are live; Arrays are not.  Applying an Array prototype method on a 
NodeList directly is guaranteed to iterate over all items if matching items 
are added while the loop is running, or not iterated over if they are 
removed before iteration has reached them.

Another problem is creating an Array instance unnecessarily.  (“[].filter” 
is just the short form.  Creation of an Array instance before filtering can 
be avoided entirely by holding the value of “Array.prototype” or 
“Array.prototype.filter” in a variable and re-using it as needed.)

-- 
PointedEars
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filter queryselectorall Andrew Poulos <ap_prog@hotmail.com> - 2016-08-06 14:25 +1000
  Re: filter queryselectorall "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-08-05 22:23 -0700
    Re: filter queryselectorall Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-06 08:16 +0200
      Re: filter queryselectorall "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-08-06 15:49 -0700
        Re: filter queryselectorall Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-07 07:08 +0200
          Re: filter queryselectorall Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2016-08-07 07:17 +0200
            Re: filter queryselectorall Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-07 07:58 +0200
          Re: filter queryselectorall "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-08-07 10:30 -0700
            Re: filter queryselectorall Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-07 21:16 +0200
              Re: filter queryselectorall "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-08-09 21:18 -0700
                Re: filter queryselectorall Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-08-15 22:02 +0200
                Re: filter queryselectorall "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-08-15 23:16 -0700
  Re: filter queryselectorall "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2016-08-06 10:28 +0200

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