On Mar 3, 6:01 am, wavded <wav...@gmail.com> wrote:
> OK this got me a significant performance bump and works in IE (there is like
> 5800 options in this multi select, don't ask me why):
Perhaps you should. 5,800 options in a select sounds like a ridiculous
number, how do users find a particular option among that many?
> Seems caching the
> elements themselves instead of the element values did the trick.
>
> var csubs = null;
> $('select[name="Subdivision"]').change(function(){
> var tsubs = $(this).val();
> if(tsubs.length > 10){
> alert('Cannot select more than 10');
> $(this).find('option:selected').attr('selected',false);
> csubs.attr('selected',true);
> } else {
> csubs = $(this).find('option:selected');
> }
> });
It would be more efficient and much more user friendly to let the user
de-select options until only 10 are selected. Then you only need to
count how many are selected, no need to unselect/reselect or remember
previously selected options.
The logic is very much simpler, an option counting function that runs
over 6,000 options in IE in 30ms can be as simple as:
function countSelected(el) {
for (var i=0, c=0, iLen=el.length; i<iLen; i++) {
c += el.options[i].selected? 1 : 0;
}
return c;
}
Presumably you only care that 10 are selected when the form is
submitted (or whatever equivalent action you have). So the fact that
at some time or other the user selected some number greater than that
is of no interest to you.
Using alerts for error messages is also user un-friendly. Provide a
hint that only 10 should be selected, then put a count in the page so
they know how many are selected. Present an in-page error if they go
over 10, so they can choose which ones to de-select.
Imagine a user who selects 10 options at the very top, then goes to
near the bottom to select one more. It would be much nicer if they can
be warned they've selected 11, and can (if they want) return to the
top and deselect one. With the posted code, they may have to go to the
top and deselect one, then go back to the bottom to select the one
that was programmatically deselected without prior warning.
--
Rob
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