js鼠标滑轮滚动事件绑定（兼容主流浏览器）

   /** Event handler for mouse wheel event.

             *鼠标滚动事件

             */  

            var wheel = function(event) {  

                var delta = 0;  

                if (!event) /* For IE. */  

                    event = window.event;  

                if (event.wheelDelta) { /* IE/Opera. */  

                    delta = event.wheelDelta / 120;  

                } else if (event.detail) {  

                    /** Mozilla case. */  

                    /** In Mozilla, sign of delta is different than in IE.

                     * Also, delta is multiple of 3.

                     */  

                    delta = -event.detail / 3;  

                }  

                /** If delta is nonzero, handle it.

                 * Basically, delta is now positive if wheel was scrolled up,

                 * and negative, if wheel was scrolled down.

                 */  

                if (delta)  

                    handle(delta);  

                /** Prevent default actions caused by mouse wheel.

                 * That might be ugly, but we handle scrolls somehow

                 * anyway, so don't bother here..

                 */  

                if (event.preventDefault)  

                    event.preventDefault();  

                event.returnValue = false;  

            }  

      

            /** Initialization code.  

             * If you use your own event management code, change it as required.

             */  

            if (window.addEventListener) {  

                /** DOMMouseScroll is for mozilla. */  

                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("鼠标滑轮向下滚动：" + delta + "次！"); // 1  

                    $("btn_next_pic").onclick(random_num);  

                    return;  

                } else {  

                    // alert("鼠标滑轮向上滚动：" + delta + "次！"); // -1  

                    $("btn_last_pic").onclick(random_num);  

                    return;  

                }  

            }