If you're a developer moving to an environments that make heavy use of asynchronous APIs, such as Node, WinRT, or Chrome packaged apps, this book how to make use of promise constructs. JavaScript routinely supports asynchronous code, setting something up with no expectation of when a response might come back. Unfortunately, writing code in that style is difficult for humans, and promises are a key set of tools for bridging that gap. This book shows you how to use these tools, and also demonstrates techniques that enable you to use features like IndexedDB or WebRTC.