Lines 15 and 16 show two different ways of running the JavaScript function replace()

AJAX works alongside Javascript and the DOM?

From Wikipedia: In computing, the same-origin policy is an important concept in the web application security model. Under the policy, a web browser permits scripts contained in a first web page to access data in a second web page, but only if both web pages have the same origin.

There are several websites that can be used to validate any JSON string you design. This site (http://jsonlint.com) caught an error in a pretty complicated string that another JSON validation site missed.