ajax请求成功后打开新窗口地址

jQuery.ajax({
      "type":"post",
      "url":"http://www.baidu.com", 
      "success":function(rel){
           if(rel.isSuccess){ 
                window.open(rel.url,"_blank");
    }
      }
});

这个url请求成功后window.open(rel.url,"_blank");会被浏览器拦截，无法打开新窗口，如果把window.open()放在ajax外面，问题就迎刃而解，代码如下：

var result="";
 
jQuery.ajax({
      "type":"post",
      "url":"http://www.baidu.com", 
      "success":function(rel){
           if(rel.isSuccess){ 
  result=rel.url;
                //window.open(rel.url,"_blank");
    }
      }
});
 
if(result.length>0){
      window.open(result,"_blank");
}