index.html

<!DOCTYPE html>
<html lang="en">
<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>Document</title>
  <style>
    #box {
      height: 100px;
      width: 100px;
      background: red;
      position: absolute;
    }
  </style>
</head>
<body>
  <div id="box" draggable="true"></div>
  <script>
    var dragdiv = document.querySelector('#box');
    var x, y;  //记录到点击时鼠标到移动框左边和上边的距离

    dragdiv.addEventListener('dragstart', function (e) {
        e.dataTransfer.effectAllowed = "move";  //移动效果
        e.dataTransfer.setData("text", '');  //附加数据，　没有这一项，firefox中无法移动
        x = e.offsetX || e.layerX;
        y = e.offsetY || e.layerY;
    }, false);

    document.addEventListener('dragover', function (e) {//取消冒泡 ,不取消则不能触发 drop事件
        e.preventDefault()|| e.stopPropagation();
    }, false);

    document.addEventListener('drop', function (e) {
        dragdiv.style.left = (e.pageX - x) + 'px';
        dragdiv.style.top = (e.pageY - y) + 'px';
        e.preventDefault() || e.stopPropagation();  //不取消，firefox中会触发网页跳转到查找setData中的内容
    }, false);
  </script> 
</body>
</html>