JS实现利用闭包判断Dom元素和滚动条的方向示例

本文实例讲述了JS实现利用闭包判断Dom元素和滚动条的方向。分享给大家供大家参考，具体

本文实例讲述了JS实现利用闭包判断Dom元素和滚动条的方向。分享给大家供大家参考，具体如下：

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 === 0) return false;
 fn(delta > 0 ? "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 / 2)) * (w > h ? (h / w) : 1),
 y = (e.clientY - wrap.offsetTop - (h / 2)) * (h > w ? (w / h) : 1),
 // 上(0) 右(1) 下(2) 左(3) 
 direction = Math.round((((Math.atan2(y, x) * (180 / Math.PI)) + 180) / 90) + 3) % 4,
 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);
 }
}