Check if Page exists

[SJamG]

Hello,

Really need some help with this code i found online to check to see if a page exists. i am kind of new to Javascript and to have this working would really help me out!

Here is the code :

<script language="javascript">

var url = "http://www.google.com";

checkUrl(url);

function checkUrl(url) {
var request = false;
if (window.XMLHttpRequest) {
request = new XMLHttpRequest;
} else if (window.ActiveXObject) {
request = new ActiveXObject("Microsoft.XMLHttp");
}

if (request) {
    request.open('GET', url, true);
     if (request.status == 200) {   //FAILING ON THIS LINE ("Unspecified Error")
       alert ("File does exist");
     }
}
alert("File does not exist");
}</script>

It seems to be failing on the .status line and it returns an Unspecified Error in the debugger.

I am using IE9 if that makes any difference. I have also tried amending the IF statement to include the readyState == 4, i dont get the error, but it doesn't work as planned.

Really appreciate any help.

SJG

[Kor]

You can not perform an AJAX request cross-domain. You need an extra, intermediate, proxy server-side code for that. See also:

http://www.troywolf.com/articles/

[SJamG]

Thanks for the very quick reply.

I put google.com in there just for illustration. I get the same error with my internal URL. The code is on a page which is on the same domain/site.

Does your advice still apply?

Thanks

[Kor]

ok. You need also to check the readyState property of the AJAX request object

if (request.readyState==4 && request.status == 200)

Another thing. To check only if a file exists, it is enough to check if the HEAD exists, thus you may use the HEAD request method instead of GET or POST. You gain speed.

[SJamG]

Interesting....

I am actually looking to open PDFs which are on a server, an example of the url would be :

http://my-server.mycompany.com/DocLibrary/Test.pdf

I did try and alter the IF statement similar to what you suggested, but it always comes back as the file exists, but i if i load the URL in a new window, i get Page cannot be displayed.

Am i going wrong somewhere?

Thanks again for the help...appreciate it.

[Kor]

And you need an event, also, which should be the onreadystatechange.

A rough AJAX request could be detailed as:

var xmlhttp;
function checkURL(url){
xmlhttp=null; // initialize the request object
// All the browsers except for the old IE
if (window.XMLHttpRequest)
  {
  xmlhttp=new XMLHttpRequest()
  xmlhttp.onreadystatechange=xmlhttpChange
  xmlhttp.open("HEAD",url,true)
  xmlhttp.send(null)
  }
// old IE
else if (window.ActiveXObject)
  {
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP")
    if (xmlhttp)
    {
    xmlhttp.onreadystatechange=xmlhttpChange
    xmlhttp.open("HEAD",url,true)
    xmlhttp.send();
    }
  }
}

function xmlhttpChange()
{
// if loaded
if (xmlhttp.readyState==4)
  {
  // if head exists "OK"
  if (xmlhttp.status==200)
    {
    alert('URL exists')
    }
  else
    {
    alert("Status is "+xmlhttp.status)
    }
  }
}

[Kor]

But I will rather send a simple AJAX request to a server-side file and let the server-side code written there(say, in PHP) to check if a file exists and to echo back the answer.

[Kor]

Here's some documentation and examples regarding AJAX:
http://www.jibbering.com/2002/4/httprequest.html

[SJamG]

Thank you all very much - It is working a treat now.

Thanks again.