js鼠标移入方向感知 Javascript实现鼠标移入方向感知

function getDir(ev, ele) {
      var l = ele.getBoundingClientRect().left;
      var t = ele.getBoundingClientRect().top;
      var w = ele.getBoundingClientRect().width;
      var h = ele.getBoundingClientRect().height;
      var x = (ev.clientX - l - w / 2) * (w > h ? (h / w) : 1);
      var y = (ev.clientY - t - h / 2) * (h > w ? (w / h) : 1);
      var deg = Math.atan2(y, x) / (Math.PI / 180);
      var d = (Math.round((deg + 180) / 90) + 3) % 4;
      return d;
      // d的值{上:0,右:1,下:2,左:3}
 }

<div id="container">
    <img src="./bg.jpg" alt="">
    <p class="ps">故事成功地将原本隐藏在黑暗中，用世界上最强大的毅力和最艰辛的努力去做最密不可宣和隐讳残酷的事情的忍者，描绘成了太阳下最值得骄傲最光明无限的职业。在岸本齐史笔下的忍者世界中，每一位年轻的忍者都在开拓着属于自己的忍道。
    </p>
</div>

*{
  margin: 0;
  padding: 0;
}

#container{
  width: 400px;
  height: 200px;
  position: relative;
  margin-top: 100px;
  margin-left: 200px;
  overflow: hidden;
  
}
#container img{
  width: 100%;
  height: 100%;
  transition: 0.5s;
}
#container p{
  width: 100%;
  height: 100%;
  padding: 10px;
  box-sizing: border-box;
  position: absolute;
  left: 0;
  /* top: 0; */
  background: rgba(0, 0, 0, .7);
  color: #ccc;
  font-size: 14px;
  line-height: 24px;
  
}
#container:hover img{
  transform: scale(1.1);
}

window.onload = function () {
      var box = document.getElementById('container');
      var ps = document.getElementsByClassName('ps');
      var pos=[
        {left:0,top:'-100%'},
        {left:'100%',top:0},
        {left:0,top:'100%'},
        {left:'-100%',top:0}
      ]
      box.onmouseenter = function(ev){
        var dir = getDir(ev,this);
        ps[0].style.transition='';
        ps[0].style.left=pos[dir].left;
        ps[0].style.top=pos[dir].top;
        setTimeout(function(){
          ps[0].style.transition='.3s';
          ps[0].style.left=0;
          ps[0].style.top=0;
        },1000/60)
      }
      box.onmouseleave = function(ev){
        var dir = getDir(ev,this);
        setTimeout(function(){
          ps[0].style.transition='';
          ps[0].style.left=pos[dir].left;
          ps[0].style.top=pos[dir].top;
        },100)
      }
    }
    function getDir(ev, ele) {
      var l = ele.getBoundingClientRect().left;
      var t = ele.getBoundingClientRect().top;
      var w = ele.getBoundingClientRect().width;
      var h = ele.getBoundingClientRect().height;
      var x = (ev.clientX - l - w / 2) * (w > h ? (h / w) : 1);
      var y = (ev.clientY - t - h / 2) * (h > w ? (w / h) : 1);
      var deg = Math.atan2(y, x) / (Math.PI / 180);
      var d = (Math.round((deg + 180) / 90) + 3) % 4;
      return d;
      // d的值{上:0,右:1,下:2,左:3}
}