使用ajax键入jQuery搜索

i'm trying to create a search where you input text into a textfield and onkeyup it will fire a function off that will send the value of the field to a page and return the results to the div container. The problem i'm having is that when someone is typing, there is a horrible lag going on. I think what's going on is that it's trying to search each letter typed in and does each request. How do i make it so that if i type into the box, wait 1/2 a second (500), if nothing is typed in, then do the ajax search,but if in that time frame another letter comes up, don't even bother with the ajax request. I've been busting my head on this and can't figure it out. All help is appreciated!i'm trying to create a search where you input t