JavaScript 实现窗口拖拽功能完整代码示例

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    .nav{
      width: 100%;
      height: 20px;
      background-color: #ccc;
    }
    .popup{
      width: 300px;
      height: 300px;
      border: 1px solid red;
      position: absolute;
      left: 50%;
      top: 50%;
      margin-left: -150px;
      margin-top: -150px;
    }
    .popup .title{
      height: 20px;
      width: 100%;
      background: deeppink;
      cursor: move;
    }
  </style>  
</head>
<body>
  <div class="nav">注册信息</div>
  <div class="popup" id="popupfather">
    <div class="title" id="popupson">我是窗口标题，可拖着我走</div>
    <div class="content">我是窗口内容</div>
  </div>
  <script>  
    var popupfather = document.getElementById('popupfather');
    var popupson = document.getElementById('popupson');

    popupson.onmousedown = function(event){
      var event = event || window.event;
      var that = this;
      var x = event.clientX - popupfather.offsetLeft - 150; //当前鼠标点击处相对于popupfather所在位置x ， -150 是处理margin值
      var y = event.clientY - popupfather.offsetTop - 150; //当前鼠标点击处相对于popupfather所在位置y
      document.onmousemove = function(event){
        var event = event || window.event;
        popupfather.style.left = event.clientX - x + "px";
        popupfather.style.top = event.clientY- y + "px";
        window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();

      }
    }
    document.onmouseup = function(){
      document.onmousemove = null;
    }
  </script>
</body>
</html>