When Tim Berners-Lee wrote the first ever web browser around 1990, it was supposed to run HTML, neither CSS nor JavaScript. Who knew that WWW will be the most powerful communication medium? Since then, there are now a number of technologies and tools that help us write the code and run it for our needs. We do a lot these days with the help of the Internet. We shop, read, learn, share, and collaborate... well, a few words are not going to suffice to explain what we do on the Internet, are they? Over the period of time, our needs have grown to a very complex level, so is the complexity of code written for websites. It's not plain HTML anymore, not some CSS style, not some basic JavaScript tweaks. That time has passed. Pick any site you visit daily, view source by opening developer tools of the browser, and look at the source code of the site. What do you see? Too much code? Too many styles? Too many scripts? The JavaScript code and CSS code is so huge to keep it as inline, and we need to keep them in different files, sometimes even different folders to keep them organized.

Now, what happens before you publish all the code live? You test it. You test each line and see if that works fine. Well, that's a programmer's job. Zero defect, that's what every organization tries to achieve. When that is in focus, testing comes into the picture, more importantly a development style that is essentially test driven. As the title for this book says, we're going to keep our focus on test-driven JavaScript development.