/*

"search"

  select Element Type-Ahead for IE/Windows by Danny Goodman (www.dannyg.com)
  This recipe first published at O'Reilly Network (www.oreillynet.com)

  Used with full permission.

*/

// 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;

}