Umm - that's not true at all.
I created a test for you to see:
http://dev.jquery.com/~john/ticket/class-speed/
In Firefox 3 I'm getting:
ID Raw: 9 ID jQuery: 22 (over 500 queries)
Class Raw: 1108 Class jQuery: 778 (over 100 queries)
In Safari 3.2 I'm getting:
ID Raw: 1 ID jQuery: 3 (over 500 queries)
Class Raw: 224 Class jQuery: 184 (over 100 queries)
So not only is jQuery's class implementation faster but the ID
searching has an approximately 0.026 milliseconds overhead - that's
2.6% of 1 millisecond per query - an absolutely acceptable figure to
be able to live with.
--John
On Mon, Feb 16, 2009 at 8:28 AM, RobG <rg...@iinet.net.au> wrote:
>
>
>
> On Feb 16, 5:30 pm, SteelRing <steelr...@gmail.com> wrote:
>> This may sound stupid to y'all jquery practitioners, but i wonder
>> which method is fastest (recommended) for selecting a cell with a
>> class in a big table (think like 1000+ rows 100+ columns):
>
> Fastest: the browser-native getElementsByClassName (recent Firefox,
> Opera, Safari) is 20 to 40 times faster than $('.className'), as a
> bonus you get a live collection.
>
> Alternatively, XPath is probably just as quick but the result isn't
> live (supported by the same set of browsers).
>
> The jQuery way is to use a CSS selector, however it is much slower
> than other methods (except perhaps in IE).
>
>
>> ("#tableid tbody tr.rowclass td.cellclass") or is it ("td.cellclass")
>> or (".cellclass").
>>
>> And how about if the cell happens to have a unique id:
>>
>> ("#tableid tbody tr#uniquerow td#uniqueid") or just ("#uniqueid")
>
> If speed really matters, getElementById is more than 7 times faster
> than $('#...') in Firefox and 4 times faster in Safari.
>
>
>> Philosophically, the question being is it better to put as much detail
>> as structurally already known by the programmer into the selector or
>> just anything goes and let jquery handle it as long as it works.
>
> There is no selector optimisation that I can see in jQuery other than
> using getElementById after discovering '#...' (and the overhead of
> discovering that means it is 4 to 6 times slower than gEBI).
>
> As a general rule, keep the selector to a minimum that concisely
> describes the element - cells must be inside table, table section and
> row elements, including those in a selector doesn't seem to help. An
> ID for the starting selector likely does.
>
> Do some testing for particular circumstances, the most efficient
> method will emerge. Don't forget to include browser-native methods
> where available.
>
>
> --
> Rob
