This is a very handy solution that is easy to implement! If you have a Select List (multiple choices) that is populated with too many choices it can be a pain to search through them. By simply adding the following code to the description of your select list it will become an auto complete & drop down field:
Auto Complete / Drop Down
<script type="text/javascript">
(function($){
new AJS.MultiSelect({
element: $("#customfield_11204"),
itemAttrDisplayed: "label",
errorMessage: AJS.params.multiselectComponentsError
});
})(AJS.$);
</script>