Add custom features to browsers old and new by writingpolyfill libraries, JavaScript plugins that take browsers beyond their nativecapabilities. In this practical fieldbook, author Brandon Satrom introducesprinciples and guidelines for polyfill development, and then walks you throughthe steps for building a complex, real-world HTML5 polyfill.

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

• Learn the current state of polyfills, including shims,opt-ins, and drop-ins
• Use principles and practices to build responsiblepolyfills that benefit the entire web development community
• Build out several features for an HTML5 Forms polyfilllibrary
• Configure a build environment and run automatedcross-browser testing
• Optimize performance, handle edge cases, and fine-tunethe speed of your polyfill
• Get examples of prollyfilling libraries that push theboundaries of the Web
• Write a sample prollyfill and compare it to currentpolyfill builds