How does the AutoSuggest feature for tags in StackOverflow avoid querying on every key stroke

Question

I am trying to implement a similar feature like the autosuggest feature for tags available below the text area on this site using Jquery. I am trying to figure out how the requests are sent after a few keystrokes and not after every keystroke. I am using a 'keyup' event to trigger the request on my app. I was made to realize that this may result in too many server hits and may affect performance.

It would be awesome if some could explain how i could implement the kind of thing stackOverflow does by not having a query run on every keyup.

Answer 1

var activity = new ActivityTimer(1000, function() {
    doSearch();
});

$("#searchBox").keyup(function(){ activity.reset() });

function ActivityTimer(deadline, callback) {
    var timer = -1;

    this.reset = function() {
        this.cancel();
        timer = setTimeout(callback, deadline);
    };

    this.cancel = function() {
        if(timer >= 0) {
            clearTimeout(timer);
            timer = -1;
        }
    };
}