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Re: Why is querySelector much slower?

From: Boris Zbarsky <bzbarsky@mit.edu>
Date: Tue, 28 Apr 2015 10:58:25 -0400
Message-ID: <553FA011.10106@mit.edu>
To: Glen Huang <curvedmark@gmail.com>
CC: public-webapps <public-webapps@w3.org>
On 4/28/15 1:58 AM, Glen Huang wrote:
> Just a quick follow up question to quench my curiosity: if I do "list[1]" and no one has ever asked the list for any element, Gecko will find the first two matching elements, and store them in the list, if I then immediately do "list[0]", the first element is returned without walking the DOM (assuming there are at least two matching elements)?

Yes, exactly.

>> querySelector("foo") and getElementsByTagName("foo")[0] can return different nodes
> Still a bit confused regarding this. If the premise is the selector only contains characters allowed in a tag name

Then in that case I _think_ those are now equivalent, though I'd have to 
check it carefully.  They didn't use to be back when 
getElementsByTagName was defined as matching on qualified name, not 

Received on Tuesday, 28 April 2015 14:58:58 UTC

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