How to query web server for existing text within a web page?

How to query web server for existing text within a web page?

I have a page on a certain domain (let's call it domain1.com) which is
checking for a version number.
Example: 1.0
Then I have another domain (let's call it domain2.com) where there is
another page.
On domain2.com, I manually update the version number by editing the text.
So say I update the number on domain2.com to 1.1
I want the page on domain1.com, on page load to query domain2.com to see
if the number is the same.
If same, then the text next to it says, "up to date!".
If different, then change the text next to it to say, "update available!".
So what is the best way to do this?
My guess is javascript or jquery.
And how do I do it?
Thanks for your help!