The worst JavaScript feature is also arguably its best. It is a remarkably ubiquitous language that has had to grow and adapt at a very fast rate. The language itself and its position within browser have precipitated this ubiquity.

JavaScript is an incredibly expressive and diverse language, with functional inspiration from Lisp and Scheme, prototypical inheritance from Self, and a C-like syntax that mirrors Java. It is a language of many paradigms. Whether you want to program in a classically object-oriented way, a prototypical way, or an entirely functional way, JavaScript has you covered. JavaScript's flexibility and its position in the broader web stack also make it incredibly accommodating to beginners. You can be immediately productive with it, and this was very much Brendan Eich's original intention. It was intended to be easy to pick up by designers and programmers alike, providing them with the power to script what was once a single-purpose platform: the browser. The once humble browser, however, has since grown into an incredibly broad and complex set of complementary abstractions.

The growth of JavaScript itself and its broad set of applications on both the client and server-side (and beyond!) has meant that the language has been pushed and pulled in a thousand different directions. An overwhelming number of frameworks, libraries, spin-off languages (for example, CoffeeScript), language extensions (for example, JSX), compilers, build tools, and other abstractions have erupted and have sought to leverage JavaScript in new and unique ways. Together, these tools form the JavaScript landscape, and it is an incredibly rich and diverse one. There are countless ways to do the same thing and, as a result, we can barely hope to do anything correctly. That is why I say that JavaScript's ubiquity is both its own worst enemy and its own greatest asset.

In this book, we'll explore foundational concepts that'll teach us to think critically about the nature of clean code and will allow us to write clean code within a language and landscape that don't always cater well code cleanness. JavaScript, if wielded well, will surprise you with its efficacy and expressiveness, and given time and effort, it can be the equal of any other language in terms of its reliability and maintainability.