How to get HTML from website that is using another login site made with javascript [on hold]

I am working on a program were i need to get the HTML from a site

But to get the HTML you need to be logged in and i can't find any real information about how to log in to a javascript site and then get the HTML from a site

Login site is http://example.com Site is using Javascript and HTML, it has 2 Inputs one that is username and one that is password and a login button and the site were i want to get the HTML from is http://example2.com

The output i want to get is the HTML from http://example2.com.