利用闭包判断Dom元素和滚动条的方向

本文收集整理自网上。

一，判断滚动条的方向，利用闭包首先保存滚动条的位置，然后当滚动时候不断更新滚动初始值，然后通过差指判断方向

     function scroll(fn) {
         //利用闭包判断滚动条滚动的方向
         var beforeScrollTop = document.body.scrollTop,
             fn = fn || function() {};
         window.addEventListener("scroll", function() {
             var afterScrollTop = document.body.scrollTop,
                 delta = afterScrollTop - beforeScrollTop;
             if (delta === ) return false;
             fn(delta >  ? "down" : "up");
             beforeScrollTop = afterScrollTop;
         }, false);
     }
     scroll(function(direction) { console.log(direction) });

二，判断鼠标的移动方向

     function direction() {
         var lastX = null,
             lastY = null;
         window.addEventListener("mousemove", function(event) {
             var curX = event.clientX,
                 curY = event.clientY,
                 direction = '';
             // console.info(event);
             // console.info(event.clientX);
             // console.info(event.clientY);
             // 初始化坐标
             if (lastX == null || lastY == null) {
                 lastX = curX;
                 lastY = curY;
                 return;
             }
             if (curX > lastX) {
                 direction += 'X右,';
             } else if (curX < lastX) {
                 direction += 'X左,';
             }
             if (curY > lastY) {
                 direction += 'Y下';
             } else if (curY < lastY) {
                 direction += 'Y上';
             }
             lastX = curX;
             lastY = curY;
             //console.info(direction);
             document.getElementById("test").innerText = direction;
         })
     }

三，判断鼠标进入和出去某Dom元素的方式，这种没有利用闭包原理

 var gaga = function(wrap) {
         var wrap = document.getElementById(wrap);
         var hoverDir = function(e) {
             var w = wrap.offsetWidth,
                 h = wrap.offsetHeight,
                 x = (e.clientX - wrap.offsetLeft - (w / )) * (w > h ? (h / w) : ),
                 y = (e.clientY - wrap.offsetTop - (h / )) * (h > w ? (w / h) : ),
                 // 上(0) 右(1) 下(2) 左(3)
                 direction = Math.round((((Math.atan2(y, x) * ( / Math.PI)) + ) / ) + ) % ,
                 eventType = e.type,
                 dirName = new Array('上方', '右侧', '下方', '左侧');
             if (e.type == 'mouseover' || e.type == 'mouseenter') {
                 wrap.innerHTML = dirName[direction] + '进入';
             } else {
                 wrap.innerHTML = dirName[direction] + '离开';
             }
         }
         if (window.addEventListener) {
             wrap.addEventListener('mouseover', hoverDir, false);
             wrap.addEventListener('mouseout', hoverDir, false);
         } else if (window.attachEvent) {
             wrap.attachEvent('onmouseenter', hoverDir);
             wrap.attachEvent('onmouseleave', hoverDir);
         }
     }

本文结束。