js写拖拽div 只能实现拖拽一遍 第二遍松开鼠标后还是会跟着鼠标走

问题遇到的现象和发生背景

js写拖拽div 只能实现拖拽一遍 第二遍松开鼠标后还是会跟着鼠标走

问题相关代码，请勿粘贴截图
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      #box1 {
        height: 100px;
        width: 100px;
        background-color: red;
        position: absolute;
      }
    </style>
    <script>
      window.onload = function () {
        var box1 = document.getElementById("box1");
        box1.onmousedown = function () {
          document.onmousemove = function (event) {
            var left = event.clientX;
            var top = event.clientY;
            box1.style.left = left + "px";
            box1.style.top = top + "px";
          };
        };
        document.onmouseup = function () {
          document.onmousemove = null;
          document.onmouseup = null;
        };
      };
    </script>
  </head>
  <body>
    <!-- 
        onmousedown
        onmouseclick
        onmouseup
     -->
    <div id="box1"></div>
  </body>
</html>
运行结果及报错内容
我的解答思路和尝试过的方法
我想要达到的结果

img

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