Delayed change jquery plugin

jquery.delayedChange.js

(function($){

  $.delayedChangeDelay = 1000;
  $.checkUpdateTime = 500;

  // Special event definition.
  $.event.special.delayedChange = {
    setup: function( params ) {

      // Add data and handlers to other events
      $(this)
        .data( 'delayedChange', {
          nextUpdate: 0,
          needsUpdate: false,
          delay: params,
          interval: window.setInterval(createCheckUpdateFor(this), $.checkUpdateTime)
        })
        .bind( 'change',  signalNeedsUpdate )
        .bind( 'keydown', signalNeedsUpdate );

    },
    teardown: function() {
      // Stop check update for this element
      var interval = $(this).data('delayedChange').interval;
      window.clearInterval(interval);

      // Remove all handlers and data
      $(this)
        .removeData( 'delayedChange' )
        .unbind( 'change',  signalNeedsUpdate )
        .unbind( 'keydown', signalNeedsUpdate );
    }
  };

  // This function is executed every time an element is modified.
  function signalNeedsUpdate ( event ) {
    // Get plugin data stored on the element.
    var elem = $(this);
    var data = elem.data( 'delayedChange' );
    var delay = data.delay || $.delayedChangeDelay;

    data.needsUpdate = true;
    data.nextUpdate = new Date().getTime() + delay;
  };

  // Creates a check update handler attached to the set element
  function createCheckUpdateFor(elem) {
    return function() {
      checkUpdate(elem);
    };
  };

  // Function invoked every X millis for checking update
  function checkUpdate(elem) {
    var elem = $(elem);

    // Get plugin data stored on the element.
    var data = elem.data( 'delayedChange' ),
      delay = data.delay || $.delayedChangeDelay,
      nextUpdate = data.nextUpdate,
      needsUpdate = data.needsUpdate;

    // If update is needed and enough time has passed, then fire the event
    if (!needsUpdate) return;
    var nowMillis = new Date().getTime();
    var diff = nowMillis - nextUpdate;

    if (diff > 0) {
      data.needsUpdate = false;
      elem.triggerHandler( 'delayedChange' );
    }
  };

})(jQuery);