关闭网页和浏览器前执行

    window.onbeforeunload = e => {
      e = e || window.event;
      if (e) {
        e.returnValue = 'close';
        //这是自己的业务逻辑
        $.ajax({
          type: "POST",
          url: "https://mock.uutool.cn/qqwwee",
          data: {
            username: '关闭'
          },
          success: function (data) {
            console.log("发出去了");
          }
        })
        //end
        return 'close';
      }
    }