Progress bar for ajax+php implementation

Using ajax+php to build progress bar is actually very simple.
ReadyState = = Status (0,1,2,3,4)
0: Request uninitialized, not called open
1: The request has been established, but has not been sent yet, send has not been called
2: The request has been sent and is being processed
3: Request is being processed, usually some data in the response can be called
4: Finished

var xmlHttp;
function Create ()
if (window. ActiveXObject)
{
XmlHttp = new ActiveXObject ("Microsoft.XMLHTTP");//ie browser
}
else if (window. XMLHttpRequest)
{
XmlHttp = new XMLHttpRequest ()//Non IE browser
}
}
function Request (URL)
{
Xmlhttp.open ("Get", "for.php?id=" +url,true);//true is asynchronous transmission
Xmlhttp.onreadystatechange = ip985;//response function
Xmlhttp.send (NULL);
}
function ip985 ()
{
if (xmlhttp.readystate==1)
{
document.getElementById (' IP985 '). InnerHTML = "Request established, ready to send ..."; IP985 sign Bit
}
if (xmlhttp.readystate==4)
{
var v = xmlhttp.responsetext;//Get content
document.getElementById (' ip985 '). InnerHTML = v;//target Web page content
}
}