JavaScript 实现鼠标移入移出方向判断逻辑

完整代码示例

<!DOCTYPE html>
<html lang="zh">
 <head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <meta http-equiv="X-UA-Compatible" content="ie=edge">
 <title></title>
 <style type="text/css">
 * {
 padding: 0;
 margin: 0;
 }
 
 .ul-box {
 width: 345px;
 margin: 20px auto;
 background-color: #f5f5f5;
 overflow: auto;
 }
 
 .li-item {
 width: 100%;
 height: 134px;
 margin-bottom: 10px;
 border-radius: 4px;
 }
 
 .li-item1 {
 background: linear-gradient(90deg, #7f90e3 0%, #8b9bff 100%);
 }
 </style>
 </head>
 <body>
 <ul id="ulBox" class="ul-box">
 <li class="li-item li-item1" onmouseleave="derEvent(event, 'leave')" onmouseenter="derEvent(event, 'enter')"></li>
 </ul>
 </body>
 <script type="text/javascript">
 /**
 * @param {Object} event 当前事件源信息
 * @return {Number} d 方向 top 0 right 1 bottom 2 left 3
 */
 function getDer(event) {
 let ele = event.target
 var d;
 var w = ele.offsetWidth,
 h = ele.offsetHeight,
 l = ele.offsetLeft,
 t = ele.offsetTop,
 x = (event.clientX - l - w / 2) * (w > h ? (h / w) : 1),
 y = (event.clientY - t - h / 2) * (h > w ? (w / h) : 1);
 d = (Math.round((Math.atan2(y, x) * (180 / Math.PI) + 180) / 90) + 3) % 4;
 return d;
 // top 0 right 1 bottom 2 left 3
 }
 /**
 * @param {Object} event 事件源信息
 * @param {Object} type 类型 leave 离开 色 enter 进入
 */
 function derEvent(event, type) {
 let d = getDer(event)
 let txt = ''
 switch (d) {
 case 0:
  txt = '上'
  break;
 case 1:
  txt = '右'
  break;
 case 2:
  txt = '下'
  break;
 case 3:
  txt = '左'
  break;
 default:
  break;
 }
 if (type === 'leave') {
 console.log(txt, '离开')
 } else {
 console.log(txt, '进入')
 }
 }
 </script>
</html>