If your JavaScript is a mess, frameworks can only do so much to help. No matter what framework, "compiles-to-JS" language, or library you use, bugs and performance concerns will always be an issue if the underlying quality of your JavaScript is poor. With this hands-on guide, you’ll learn how test and refactor your existing code to help reduce complexity, improve readability, and gain confidence in the codebase. Author Evan Burchard shows you how to identify areas of bad code, and then takes you through several refactoring methods for improving them. Techniques range from renaming variables to applying principles of functional and object-oriented programming. If you’re motivated to write better JavaScript code either on the frontend or backend, this book is a must. Use refactoring to restructure existing code, without changing its behavior Learn the relationship between refactoring and quality Explore the many versions of JavaScript in use today Create automated tests to confirm that your code works, and find bugs that slip through Learn how to refactor simple JavaScript structures, functions, and objects Refactor your codebase by applying object-oriented and functional programming principles Examine methods for refactoring asynchronous JavaScript