(The book has two parts. The first part gives the basic knowledge of the object-oriented features needed to implement a specific design pattern, mainly including interface, encapsulation, information hiding, inheritance and single pattern. The second part focuses on various specific design patterns and their application in JavaScript language. It mainly introduces several common patterns, such as factory pattern, bridge pattern, combination pattern, facade pattern and so on. In order to make the examples in each chapter as close to the practical application as possible, the book also lists some of the most common tasks of JavaScript programmers, and then uses design patterns to make their solutions more modular, more efficient and easier to maintain. More theoretical examples are used to illustrate some points.This book is suitable for web front-end developers at all levels to read and refer to, as well as server-side programmers with C + + / Java / c# background.)