If we need any further motivation that JavaScript is no longer just for scriptable web pages, look no further than NodeJS. It doesn't require the full browser environment, just the V8 JavaScript engine. Node was created primarily as a backend server environment, but it still serves as a great showcase for how far JavaScript as a language has come. In the same vein, we want our code to be portable, running with any backend infrastructure we can throw at it.

In this section, we'll look at the reasons why we want to loosen the coupling between our frontend JavaScript code, and the APIs it talks to in the backend. We'll then introduce the first steps to mocking APIs, negating the need for a backend entirely.