JavaScript实现类似拉勾网的鼠标移入移出效果

<ul>
 <li>
 <div class="bg">
 <p>JS</p>
 </div>
 </li>
 .....
</ul>

function pointTo(element, e) {
 var elementBox = element.getBoundingClientRect();
 return {
 x: e.clientX - elementBox.left,
 y: e.clientY - elementBox.top
 };
}

function startPoint(element){
 var x = 0,y = 0;
 while(element != null) {
 x += element.offsetLeft;
 y += element.offsetTop;
 element = element.offsetParent;
 }
 return {
 x: x,
 y: y
 }
}

offsetHeight与offsetWidth

/* options参数: obj: 运动的对象 speed: 运动的持续时间(可选) changeStyle: 改变的属性，这里可能多个，所以采用函数的方式(可选) callback: 回调函数(可选) */
 function animation(options){
 if(!options.obj) {
 return false;
 }
 //设置默认持续时间
 options.speed = options.speed || '.5s';
 options.obj.style.transition = "all " + options.speed + " ease-in-out";
 
 options.changeStyle.call(options.obj);
 
 var flag = false;
 options.obj.addEventListener('transitionend',function(){
 //这里主要由于transitionend在每个属性的动画执行完多会走一遍，所以我们要让它只执行一次。
 if(!flag) {
 
 options.callback && options.callback();
 }
 },false);
 }

function getDirection(element,startPoint,pagePoint){
 var halfWidth = element.offsetWidth / 2,halfHeight = element.offsetHeight / 2;
 //得到中心点
 var center = {
 x: startPoint.x + halfWidth,
 y: startPoint.y + halfHeight
 }
 //得到鼠标偏离中心点的距离
 var disX = pagePoint.x - center.x;
 var disY = pagePoint.y - center.y;
 if(disY < 0 && Math.abs(disY / disX) >= 1) {
 //上方
 return 1;
 }
 else if(disY > 0 && Math.abs(disY / disX) >= 1) {
 //下
 return 2;
 }
 else if(disX < 0 && Math.abs(disY / disX) < 1) {
 //左
 return 3;
 }
 else {
 //右
 return 4;
 }
}

/* options中的参数: 触发事件的载体: targetElement 执行动画的载体: animationElement */
 function HoverAction(options) {
 if(!options.targetElement || !options.animationElement) {
 return false;
 }
 this.targetElement = options.targetElement;
 this.animationElement = options.animationElement;
 this.timeId = null;
 this.speed = "0.3s";
 }
 HoverAction.prototype.addEvent = function() {
 //保存this的指向
 var _this = this;
 _this.targetElement.addEventListener('mouseenter',function(e){
 //得到鼠标的坐标
 var point = {
 x: e.pageX,
 y: e.pageY
 }
 console.log(point);
 //获得方向
 var dir = getDirection(_this.targetElement,startPoint(_this.targetElement),point);
 clearTimeout(_this.timeId);
 //取消过渡动画(防止重置动画载体位置时触发过渡效果)
 _this.animationElement.style.transition = "";
 //得到运动的方向，要确定动画载体的开始位置
 switch(dir){
 case 1:
 _this.animationElement.style.top = "-100%";
 _this.animationElement.style.left = "0";
 break;
 case 2:
 _this.animationElement.style.top = "100%";
 _this.animationElement.style.left = "0";
 break;
 case 3:
 _this.animationElement.style.top = "0";
 _this.animationElement.style.left = "-100%";
 break;
 case 4:
 _this.animationElement.style.top = "0";
 _this.animationElement.style.left = "100%";
 break;
 }
 //异步执行
 _this.timeId = setTimeout(function(){
 animation({
 obj: _this.animationElement,
 speed: _this.speed,
 changeStyle: function(){
 this.style.top = "0";
 this.style.left = "0";
 }
 });
 },20);
 },false);
 _this.targetElement.addEventListener('mouseleave',function(e){
 var left,top;
 var point = {
 x: e.pageX,
 y: e.pageY
 }
 clearTimeout(_this.timeId);
 _this.animationElement.style.transition = "";
 var dir = getDirection(_this.targetElement,startPoint(_this.targetElement),point);
 switch(dir) {
 case 1:
 top = '-100%';
 left = '0';
 break;
 case 2:
 top = '100%';
 left = "0";
 break;
 case 3:
 left = "-100%";
 top = "0";
 break;
 case 4:
 left = "100%";
 top = "0";
 break;
 }
 _this.timeId = setTimeout(function(){
 animation({
 obj: _this.animationElement,
 speed: _this.speed,
 changeStyle: function(){
 this.style.top = top;
 this.style.left = left;
 }
 });
 },20);
 },false);
 
 }