jquery mousewheel

<script type="text/javascript" src="http://code.jquery.com/jquery-1.7.1.min.js"></script>
<script type="text/javascript">
(function($) {
  
var types = ['DOMMouseScroll', 'mousewheel'];
  
$.event.special.mousewheel = {
    setup: function() {
        if ( this.addEventListener ) {
            for ( var i=types.length; i; ) {
                this.addEventListener( types[--i], handler, false );
            }
        } else {
            this.onmousewheel = handler;
        }
    },
      
    teardown: function() {
        if ( this.removeEventListener ) {
            for ( var i=types.length; i; ) {
                this.removeEventListener( types[--i], handler, false );
            }
        } else {
            this.onmousewheel = null;
        }
    }
};
  
$.fn.extend({
    mousewheel: function(fn) {
        return fn ? this.bind("mousewheel", fn) : this.trigger("mousewheel");
    },
      
    unmousewheel: function(fn) {
        return this.unbind("mousewheel", fn);
    }
});
  
  
function handler(event) {
    var orgEvent = event || window.event, args = [].slice.call( arguments, 1 ), delta = 0, returnValue = true, deltaX = 0, deltaY = 0;
    event = $.event.fix(orgEvent);
    event.type = "mousewheel";
      
    // Old school scrollwheel delta
    if ( event.wheelDelta ) { delta = event.wheelDelta/120; }
    if ( event.detail     ) { delta = -event.detail/3; }
      
    // New school multidimensional scroll (touchpads) deltas
    deltaY = delta;
      
    // Gecko
    if ( orgEvent.axis !== undefined && orgEvent.axis === orgEvent.HORIZONTAL_AXIS ) {
        deltaY = 0;
        deltaX = -1*delta;
    }
      
    // Webkit
    if ( orgEvent.wheelDeltaY !== undefined ) { deltaY = orgEvent.wheelDeltaY/120; }
    if ( orgEvent.wheelDeltaX !== undefined ) { deltaX = -1*orgEvent.wheelDeltaX/120; }
      
    // Add event and delta to the front of the arguments
    args.unshift(event, delta, deltaX, deltaY);
      
    return $.event.handle.apply(this, args);
}
  
})(jQuery);
$(function(){
 
    $('#dv').mousewheel(function(){alert(123)});
 
})
</script>
<div style="height:1000px" id="dv">123</div>