another cool javascript

/***************
"search"
select Element Type-Ahead for IE/Windows by Danny Goodman (www.dannyg.com)
A bonus recipe for readers of O'Reilly's
"JavaScript & DHTML Cookbook"
This recipe first published at O'Reilly Network (www.oreillynet.com)
For full implementation notes, read the article.
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// global storage object for type-ahead info, including reset() method var typeAheadInfo = {last:0,
accumString:"",
delay:500,
timeout:null,
reset:function() {this.last=0; this.accumString=""}
};
// function invoked by select element's onkeydown event handler function typeAhead() {
// limit processing to IE event model supporter; don't trap Ctrl+keys if (window.event && !window.event.ctrlKey) {
// timer for current event var now = new Date();
// process for an empty accumString or an event within [delay] ms of last if (typeAheadInfo.accumString == "" || now - typeAheadInfo.last < typeAheadInfo.delay) {
// make shortcut event object reference var evt = window.event;
// get reference to the select element var selectElem = evt.srcElement;
// get typed character ASCII value var charCode = evt.keyCode;
// get the actual character, converted to uppercase var newChar = String.fromCharCode(charCode).toUpperCase();
// append new character to accumString storage typeAheadInfo.accumString += newChar;
// grab all select element option objects as an array var selectOptions = selectElem.options;
// prepare local variables for use inside loop var txt, nearest;
// look through all options for a match starting with accumString for (var i = 0; i < selectOptions.length; i++) {
// convert each item's text to uppercase to facilitate comparison // (use value property if you want match to be for hidden option value) txt = selectOptions[i].text.toUpperCase();
// record nearest lowest index, if applicable nearest = (typeAheadInfo.accumString > txt.substr(0, typeAheadInfo.accumString.length)) ? i : nearest;
// process if accumString is at start of option text if (txt.indexOf(typeAheadInfo.accumString) == 0) {
// stop any previous timeout timer clearTimeout(typeAheadInfo.timeout);
// store current event's time in object typeAheadInfo.last = now;
// reset typeAhead properties in [delay] ms unless cleared beforehand typeAheadInfo.timeout = setTimeout("typeAheadInfo.reset()", typeAheadInfo.delay);
// visibly select the matching item selectElem.selectedIndex = i;
// prevent default event actions and propagation evt.cancelBubble = true;
evt.returnValue = false;
// exit function return false;
}
}
// if a next lowest match exists, select it if (nearest != null) {
selectElem.selectedIndex = nearest;
}
} else {
// not a desired event, so clear timeout clearTimeout(typeAheadInfo.timeout);
}
// reset global object typeAheadInfo.reset();
}
return true;
}

<select onkeydown="typeAhead()">
<option value="tony">tony
<option value="your mom">your mom
<option value="your dad">your dad
<option value="krishna">krishna
<option value="rocky">rocky
</select>