js怎么实现实时监控 一个变量的值进行相应的操作

呵呵 附上段代码 希望对有相同问题的朋友有所帮助  var setin;
        var ck;
        var outTime = 0;
          function Sends() { 
              $.ajax({
                  type: "post",
                  url: "Login.aspx/GetGroup",
                  async: false,
                  contentType: "application/json; charset=utf-8",
                  dataType: "json",
                  success: function (result) {
                     num=result.d;
                  }             });
             if (num.lenght < 0) {
                 alert('未获取到可用设备!')
                 return;
             }
                  
                SendPosts(num);
                  outTime = 0;
                setin = setInterval(CkBox, 100); 
            }   
          
            function CkBox() {
                outTime++;
                ck = CanClass.CKPost(num);
                if (ck > 0) {
                    window.clearInterval(setin);
                    UpdateStates();
                } else {
                 
                    if (parseInt(outTime) > 1000) 
                    {
                        window.clearInterval(setin);
                        alert('超时');
                    }
                    
                }  
            }
            function UpdateStates() {
                $.ajax({
                    type: "post",
                    url: "Login.aspx/SetPost",
                    async: false,
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (result) {
                        if (result.d > 0) {
                            CanClass.UpdateScrn("欢迎您", 2);
                            alert('成功!');
                        } else {
                            CanClass.UpdateScrn("失败", 2);
                            alert('失败!');                        }                    }
                });
         }