keyup_delay.js

var delay = (function(){
  var timer = 0;
  return function(callback,param, ms){
    clearTimeout (timer);
    timer = setTimeout(function(){
        callback(param);
    }, ms);
  };
})();

//example
$('input').keyup(function() {
    delay(function(){
      alert('Time elapsed!');
    }, 1000 );
});