Trying to add delay to jQuery AJAX request

Question

I am trying to delay an AJAX request so that it is sent out 2-3 seconds after the LAST keyup of an input cell.
So far I have managed to delay the requests, but after 2-3 seconds I get one request sent for every keyup in the field...
How can I make jQuery cancel the first ones and just send the last keyup?
Here's the code so far:

$('#lastname').focus(function(){
          $('.terms :input').val(""); //clears other search fields
}).keyup(function(){
    caps(this); //another function that capitalizes the field
    $type = $(this).attr("id"); // just passing the type of desired search to the php file
        setTimeout(function(){ // setting the delay for each keypress
                ajaxSearchRequest($type); //runs the ajax request

        }, 1000);
});

This code above, waits 1 sec then sends 4-5 AJAX requests depending on keypresses. I just want one sent after the last keyup
I have found some similar solutions in StackOverflow that use Javascript, but I have not been able to implement them to my project due to my small knowledge of programming.

[SOLVED] Final working code, thanks to @Dr.Molle:

$('#lastname').focus(function(){
          $('.terms :input').val("");
}).keyup(function(){
    caps(this);
    $type = $(this).attr("id");

    window.timer=setTimeout(function(){ // setting the delay for each keypress
            ajaxSearchRequest($type); //runs the ajax request

        }, 3000);

}).keydown(function(){clearTimeout(window.timer);});

Here's the ajaxSearchRequest code:

function ajaxSearchRequest($type){
                var ajaxRequest2;  // The variable that makes Ajax possible!

                try{
                  // Opera 8.0+, Firefox, Safari
                  ajaxRequest2 = new XMLHttpRequest();
                }catch (e){
                  // Internet Explorer Browsers
                  try{
                     ajaxRequest2 = new ActiveXObject("Msxml2.XMLHTTP");
                  }catch (e) {
                     try{
                    ajaxRequest2 = new ActiveXObject("Microsoft.XMLHTTP");
                     }catch (e){
                    // Something went wrong
                    alert("Browser error!");
                    return false;
                     }
                  }
                }

                ajaxRequest2.onreadystatechange = function(){
                  if(ajaxRequest2.readyState == 4){

                        $result = ajaxRequest2.responseText;
                        $('#resultcontainer').html($result);

                    }}


                var searchterm = document.getElementById($type).value;


                var queryString ="?searchterm=" + searchterm +"&type=" +$type;


                if(searchterm !== ""){

                ajaxRequest2.open("GET", "searchrequest.php" + 
                                 queryString, true);
                ajaxRequest2.send(null);
                }
        }

Answer 1

store the timeout in a variable, so you will be able to clear recent timeouts:

clearTimeout(window.timer);
window.timer=setTimeout(function(){ // setting the delay for each keypress
                ajaxSearchRequest($type); //runs the ajax request

        }, 3000);