如何让'keydown'事件阻止'keyup'事件？

Question

I have a zip code resolver and I'm using a keyup event handler to track when the length of the input reaches 5 then query the server to resolve the zip code. But I want to keep the script from being unnecessarily being called, so I was wonder if there were a way to track a keydown event and stop the keyup event when there is already 5 characters in the textbox (which would indicate that a query has probably already been submitted), if there were a way to stop the keyup event handler after? I know this is kind of a weird question so feel free to ask questions. Here kind of a layout of what I'm talking about:

$('#zip_resolver').live('keydown', function(event){
    if($(this).val().length==5){
        //STOP KEYUP EVENT
    }else{
        //DO NOTHING
    }
});
$('#zip_resolver').live('keyup', function(){
    if($(this).val().length==5){
        //SEND RESOLVE REQUEST
    }
});

Answer 1

You can just enforce that the keydown was 4: http://jsfiddle.net/rkw79/H7PhT/1/

$('#zip_resolver').live('keydown', function(event){
   wasfour = (4 == $(this).val().length);
});
$('#zip_resolver').live('keyup', function(){
    if($(this).val().length==5  && wasfour){
        //SEND RESOLVE REQUEST
    }
});

Answer 2

Instead of a keydown event, how about having a boolean flag that you check in keyup to decide if you have to do a resolve?

Something like:

if (doresolve && length == 5) {
   resolve();
   doresolve = false;
} else if (!doresolve && length <> 5) {
   doresolve = true;
}

That way, when you edit the field, the resolver check is redone.