常用的3秒钟跳到哪儿里

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var i = 2; var str= document.getElementById('msg').innerHTML;       //alert(str.indexOf('上传头像成功'));       if(document.getElementById('step3').style.display=='block' && str.indexOf('上传头像成功')>0 )     {         setTimeout("window.location='user_recommend.php'",3000);         setInterval("time()",1000);     }           function time()     {         document.getElementById('time').innerHTML = i;         if (i>0)         {             i--;         }               //alert(i);     }