autocomplete in YUI is very slow in IE6 on large dataset

Question

Trying to use autocomplete functionality of YUI, we ran into the fact that it's extremely slow on IE6 for a datasource containing 30000 items (when trying to type in an autocomplete field, it takes several MINUTES for IE to respond).

However, the same exact code works pretty much real-time in IE8.

Are we doing something wrong? Can we optimize this somehow? Is IE6+YUI autocomplete not designed for such large datasets?

Here's our code initializing the autocompleter:

Y.namespace( 'YAHOO.program' );
Y.program.AllTreeItemsArr = new Array();
// Populate the array with 30000 elements
Y.program.BasicLocal = function() {
        var oDS = new YU.LocalDataSource(Y.program.AllTreeItemsArr);
        oDS.responseSchema = {fields : ["portfolio"]};
        var oAC = new Y.widget.AutoComplete("selected"
                                          , "autocomplete_container", oDS);
        oAC.prehighlightClassName = "yui-ac-prehighlight";
        oAC.useShadow = true;
        oAC.typeAhead = true;
        oAC.queryDelay = .05;
        oAC.typeAheadDelay = .5;

        return {
            oDS: oDS,
            oAC: oAC
        };
     }();

And here's the HTML to use it:

    <span id="port_autocomplete" class="yui-skin-sam" style='position: relative;'>
         <input type='text' id='selected' maxlength=10 name='selected'
                value='' isSelected=1 onkeyup="searchOnEnter();">
         <div id="autocomplete_container" style="position: absolute"></div>
    </span>

The searchOnEnter function is a standard "catch a keypress and execute a search JS function if key == 13".

Answer 1

The obvious answer is that IE has a slow JS engine, and 30000 records is a lot of data. However, the filtering operation does include one call that may be the root of your trouble. Try this patch out and see if it makes a difference:

http://gist.github.com/316358