Add custom features to browsers old and new by writing polyfill libraries, JavaScript plugins that take browsers beyond their native capabilities. In this practical fieldbook, author Brandon Satrom introduces principles and guidelines for polyfill development, and then walks you through the steps for building a complex, real-world HTML5 polyfill.

You'll also explore the future of polyfilling—or prollyfilling—that will enable you to test and work with emerging concepts, often ahead of browser vendors. By the time you finish this book, you'll have the tools and hands-on experience you need to build reliable polyfills for today's and tomorrow's Web.