Js mouse wheel scroll event binding simple example of of compatible with mainstream browsers

  
        var wheel = function(event) {  
            var delta = 0;  
            if (!event)   
                event = window.event;  
            if (event.wheelDelta) { /* IE/Opera. */  
                delta = event.wheelDelta / 120;  
            } else if (event.detail) {  
                  
                  
                delta = -event.detail / 3;  
            }  
              
            if (delta)  
                handle(delta);  
              
            if (event.preventDefault)  
                event.preventDefault();  
            event.returnValue = false;  
        }  

          
        if (window.addEventListener) {  
              
            window.addEventListener('DOMMouseScroll', wheel, false);  
        }  
        /** IE/Opera. */  
        window.onmousewheel = document.onmousewheel = wheel;  

        /** This is high-level function. 
         * It must react to delta being more/less than zero. 
         */  
        var handle = function(delta) {  
            var random_num = Math.floor((Math.random() * 100) + 50);  
            if (delta < 0) {  
                // alert(" Mouse pulley scroll down: " + delta + " Times! "); // 1  
                $("btn_next_pic").onclick(random_num);  
                return;  
            } else {  
                // alert(" Mouse pulley scroll up: " + delta + " Times! "); // -1  
                $("btn_last_pic").onclick(random_num);  
                return;  
            }  
        }