12. Abstracting Browser Differences: Ajax

Ajax, (asynchronous JavaScript and XML) is a marketing term coined to describe client technologies used to create rich internet applications, with the XMLHttpRequest object at the center stage. It’s used heavily across the web, usually through some JavaScript library.

In this chapter we will get to know XMLHttpRequest better by implementing our own higher level API using test-driven development. Doing so will allow us to touch ever so lightly on the inner workings of an “ajax call”; it will teach us how to use test-driven development to abstract browser inconsistencies; and most importantly, it will give us an introduction to the concept of stubbing.