Question

Two good examples would be google and facebook.

I have lately pondered the motivation for this approach. My best guess would be it almost completely separates the logic between your back-end language and the markup. Building up an array to send over in JSON format seems like a tidy way to maintain code, but what other elements am I missing here?

What are the advantages / disadvantages to this approach, and why are such large scale companies doing it?

Answer 1

The main disadvantage is that you have some pain with content indexation of your site.

For Google you can somewhere solve the problem by using Crawling scheme. Google supports crawling that allows you to index dynamically (without page reload) generated content of your page.

To do this your virtual links must be addresses like so: http://yoursite.com/#!/register/. In this case Google requests to http://yoursite/register/ to index content of the address.

When clicking on virtual link there is no page reload. You can provide this by using onclick:

<a href='http://yoursite.com/#!/register/' onclick='showRegister()'>Register</a>

Virtual advantage is that content of a page changed without reloading of the page. In my practice I do not use Javascript generation to do this because I build my interface in fixed positions. When page reloads user does not notice anything because elements of the interface appears in expected places.

So, my opinion that using of dynamic page generation is a big pain. I think Google did it not to separate markup and backend (it’s not a real problem, you can use complex structure of backend-frontend to do that) but to use advantages of convenient and nice representation for users.