regex - Open webpage and parse it using JavaScript

Question

I know JavaScript can open a link in a new window but is it possible to open a webpage without opening it in a window or displaying it to the user? What I want to do is parse that webpage for some text and use it as variables.

Is this possible without any help from server side languages? If so, please send me in a direction I can achieve this.

Thanks all

Answer 1

You can use an XMLHttpRequest object to do this. Here's a simple example

var req = new XMLHttpRequest();  
req.open('GET', 'http://www.mydomain.com/', false);   
req.send(null);  
if(req.status == 200)  
   dump(req.responseText);

Once loaded, you can perform your parsing/scraping by using javascript regular expressions on the req.responseText member.

More detail...

In practice you need to do a little more to get the XMLHttpRequest object in a cross platform manner, e.g.:

var ua = navigator.userAgent.toLowerCase();
if (!window.ActiveXObject)
  req = new XMLHttpRequest();
else if (ua.indexOf('msie 5') == -1)
  req = new ActiveXObject("Msxml2.XMLHTTP");
else
  req = new ActiveXObject("Microsoft.XMLHTTP");

Or use a library...

Alternatively, you can save yourself all the bother and just use a library like jQuery or Prototype to take care of this for you.

Same-origin policy may bite you though...

Note that due to the same-origin policy, the page you request must be from the same domain as the page making the request. If you want to request a remote page, you will have to proxy that via a server side script.

Another possible workaround is to use Flash to make the request, which does allow cross-domain requests if the target site grants permission with a suitably configured crossdomain.xml file.

Here's a nice article on the subject of the same-origin policy:

• Same-Origin Policy Part 1: Why we’re stuck with things like XSS and XSRF/CSRF