> Opening a webpage,
> Clicking on links,
> Modifying the content...

SlimerJS is useful to do functional tests, page automation, network monitoring, screen capture, web scraping etc.

SlimerJS is similar to PhantomJs, except that it runs on top of Gecko, the browser engine of Mozilla Firefox, instead of Webkit, and it can be headless or not.

Read more about SlimerJS...

Simple example
var webpage = require('webpage').create();
webpage
  .open('http://somewhere') 
  .then(function(){ 
    
    webpage.viewportSize =
        { width:650, height:320 };
    webpage.render('page.png',
                   {onlyViewport:true});
    
    return webpage.open('http://somewhere2');
  })
  .then(function(){
    
    webpage.sendEvent("click", 5, 5,
                        'left', 0);
    slimer.exit()
  });