(Many people have the impression that JavaScript is an easy to learn and easy to use language. JavaScript language itself has many complex concepts. Users of the language can write fully functional applications without in-depth understanding of these concepts. As we all know, these complex and subtle concepts are the essence of the language. Even experienced JavaScript developers can't really understand them without careful study. In this book, we will face the current general trend that JavaScript developers do not understand, and have an in-depth understanding of the internal mechanism of the language.This book is suitable for beginners of JavaScript language and experienced JavaScript developers.)