keyof与Object.keys略有相似，只是 keyof 是取 interface 的键 ， 而且 keyof 取到键后会保存为联合类型。

interface iUserInfo {
  name: string;
  age: number;
type keys = keyof iUserInfo;
keyof 的简单栗子
 
我们有这样一个需求，实现一个函数 getValue 取得对象的 value。在未接触 keyof 时，我们一般会这样写：
 
function getValue(o: object, key: string) {
  return o[key];
const obj1 = { name: '张三', age: 18 };
const name = getValue(obj1, 'name');
但是，这样写就丧失了 ts 的优势：
 
无法确定返回值类型
无法对 key 进行约束，可能会犯拼写的错误
 
这时我们可以使用 keyof 来增强 getValue 函数的类型功能。
 
使用 keyof 后我们可以看到，可以完整的提示可以输入的值，当拼写错误时也会有清晰的提示。
 
function getValue<T extends Object, K extends keyof T>(o: T, key: K): T[K] {
  return o[key];
const obj1 = { name: '张三', age: 18 };
const a = getValue(obj1, 'hh');
in用于取联合类型的值。主要用于数组和对象的构造。
 
但切记不要用于 interface，否则会出错
 
type name = 'firstName' | 'lastName';
type TName = {
  [key in name]: string;
                    keyof定义keyof与Object.keys略有相似，只是 keyof 是取 interface 的键，而且 keyof 取到键后会保存为联合类型。interface iUserInfo {  name: string;  age: number;}type keys = keyof iUserInfo;keyof 的简单栗子我们有这样一个需求，实现一个函数 getValue 取得对象的 value。在未接触 keyof 时，我们一般会这样写：fu.
				
Advanced TypeScript Programming Projects: Build 9 different apps with TypeScript 3 and JavaScript frameworks such as Angular, React, and Vue
Gain in-depth knowledge of TypeScript and the latest ECMAScript standards by building robust web applications across different domains
Key Features
Apply the cutting-edge features of TypeScript 3.0 to build high-performance, maintainable applications
Learn through practical examples of using TypeScript with popular frameworks, such as Angular and React
Focus on building high-quality applications that are modular, scalable and adaptable
Book Description
With the demand for ever more complex websites, the need to write robust, standard-compliant JavaScript has never been greater. TypeScript is modern JavaScript with the support of a first-class type system, which makes it simpler to write complex web systems. With this book, you'll explore core concepts and learn by building a series of websites and TypeScript apps.
You'll start with an introduction to TypeScript features that are often overlooked in other books, before moving on to creating a simple markdown parser. You'll then explore React and get up to speed with creating a client-side contacts manager. Next, the book will help you discover the Angular framework and use the MEAN stack to create a photo gallery. Later sections will assist you in creating a GraphQL Angular Todo app and then writing a Socket.IO chatroom. The book will also lead you through developing your final Angular project which is a mapping app. As you progress, you'll gain insights into React with Docker and microservices. You'll even focus on how to build an image classification program with machine learning using TensorFlow. Finally, you'll learn to combine TypeScript and C# to create an ASP.NET Core-based music library app.
By the end of this book, you'll be able to confidently use TypeScript 3.0 and different JavaScript frameworks to build high-quality apps.
				
Key Features
This step-by-step guide will would demonstrate all the important design patterns in practice
This book is the only documentation on the market focusing on design patterns in TypeScript
This book is packed with rich examples that will improve your efficiency and encourage code reuse
Book Description
In programming, there are several problems that occur frequently. To solve these problems, there are various repeatable solutions that are known as design patterns. Design patterns are a great way to improve the efficiency of your programs and improve your productivity.
This book is a collection of the most important patterns you need to improve your applications’ performance and your productivity. The journey starts by explaining the current challenges when designing and developing an application and how you can solve these challenges by applying the correct design pattern and best practices.
Each pattern is accompanied with rich examples that demonstrate the power of patterns for a range of tasks, from building an application to code testing. We’ll introduce low-level programming concepts to help you write TypeScript code, as well as work with software architecture, best practices, and design aspects.
What you will learn
Understand the challenges and implications of developing an enterprise application
Install and configure the necessary tools in order to start developing an application
Identify the challenges when developing an application
Apply GoF patterns in an application with a testing approach
Use and utilize design patterns while developing a TypeScript application or during JavaScript application development
Reference to SOLID principles and what their benefits do to your projects
Apply various principles in a TypeScript application
Improve code quality and development speed
About the Author
Vilic Vane is a JavaScript engineer with over 8 years of experience in web development. He started following the TypeScript project since it went public, and he’s also a contributor of the project. He is now working at Ruff, a startup company building an IoT platform that runs JavaScript on embedded devices.
Table of Contents
Chapter 1: Tools and Frameworks
Chapter 2: The Challenge of Increasing Complexity
Chapter 3: Creational Design Patterns
Chapter 4: Structural Design Patterns
Chapter 5: Behavioral Design Patterns
Chapter 6: Behavioral Design Patterns: Continuous
Chapter 7: Patterns and Architectures in JavaScript and TypeScript
Chapter 8: SOLID Principles
Chapter 9: The Road to Enterprise Application
克隆存储库
git clone --depth=1 https://github.com/StefanKjartansson/ts-express-cloud-function-template.git <project>
cd <project>
yarn install
使用<project>和相关信息更新package.json。
配置服务和部署管道
在GCP中，为您的项目启用云功能
导出具有云功能开发人员权限的服务帐户密钥
在配置项目并添加以下环境变量：
 GCP_AUTH=Value should be base64 encoded service account key "base64 <your>"
GCP_PROJECT=Your project id from GCP.
GCP_FUNCTION=The name of the function in GCP.
				
很早就听过 TypeScript，当时自己试了下觉得挺简单的，就是给数据声明一个类型提高可读和维护性，不过当时 TS 还不盛行，项目也没机会用到就一直落着，随着 TS 不断普及，许多项目都开始引入了 TS，这不最近在 github 看到一些 TS 代码后，心里开始吐槽：
这好好的非要给 JS 装饰的这么花里胡哨的？我都认不出来这是什么语言了，你确定这是提升 JS 语言可读性而不是添乱？有同学跟我一样的请举个手！后来静下心来想了想，既来之则安之，与其吐槽，不如静下心来好好重温下 TS ，在这期间也提取了一些有
				
类型保护是可执行运行时检查的一种表达式，用于确保该类型在一定的范围内。换句话说，类型保护可以保证一个字符串是一个字符串，尽管它的值也可以是一个数值。
类型保护与特性检测并不是完全不同，其主要思想是尝试检测属性、方法或原型，以确定如何处理值。目前主要有四种的方式来实现类型保护,这里主要演示使用in关键字进行类型守卫；
interface YuZhouK{
    name:string,
    dis:number
interface YuZhouV{
    name:string,
				
Key Features
Start with the basics, then enhance your knowledge with in-depth discussions on language features, third-party libraries, design patterns and more
Practical examples that show how to use TypeScript with popular frameworks, including Backbone, Angular 2, React, Aurelia, Node and others
Focus on test-driven development to build high quality applications that are modular, scalable and adaptable
Book Description
The TypeScript language, compiler and open-source development toolset brings JavaScript development up to the enterprise level. It allows us to use ES5, ES6 and ES7 JavaScript language features today - including classes, interfaces, generics, modules and more. It's simple typing syntax enables building large, robust applications using object-oriented techniques and industry standard design principles.
Packed with practical, real-world examples, this book is a guide to bringing the benefits of strongly typed, object-oriented programming and design principles into the JavaScript development space. Starting with core language features, and working through more advanced topics such as generics and asynchronous programming techniques, you will learn how to gain maximum benefit from your JavaScript development with TypeScript. With a strong focus on test-driven development, and coverage of many popular and in-demand JavaScript frameworks, you can fast-track your TypeScript knowledge to a professional level. By the end of this book, you will be able to confidently build TypeScript applications, whether you are targeting Angular 2, Aurelia, React, Backbone, Node or any other JavaScript framework.
What you will learn
Gain an insight into core and advanced TypeScript language features including inheritance, generics, asynchronous programming techniques, promises, decorators and more
Integrate your existing JavaScript libraries and third-party frameworks by writing and using declaration files
Target popular JavaScript frameworks such as jQuery, Backbone, Angular 2, Aurelia, React, Node and Express
Create extensive test suites for your application, including unit testing, integration testing and browser automation with Jasmine, Protactor and Selenium
Organize your application code using modules, AMD loaders, Require and SystemJs
Explore advanced object-oriented design principles including Dependency Injection and Domain Events
Understand and compare the various MVC implementations in Aurelia, Angular 2 and React
Build a complete single-page web application that incorporates css animations to enhance your customer's browsing experience
Table of Contents
Chapter 1. TypeScript - Tools and Framework Options
Chapter 2. Types, Variables, and Function Techniques
Chapter 3. Interfaces, Classes, and Inheritance
Chapter 4. Decorators, Generics, and Asynchronous Features
Chapter 5. Writing and Using Declaration Files
Chapter 6. Third-Party Libraries
Chapter 7. TypeScript Compatible Frameworks
Chapter 8. Test Driven Development
Chapter 9. Testing Typescript Compatible Frameworks
Chapter 10. Modularization
Chapter 11. Object-Oriented Programming
Chapter 12. Dependency Injection
Chapter 13. Building Applications
Chapter 14. Let's Get Our Hands Dirty
				
Mastering TypeScript - Second Edition by Nathan Rozentals
English | 6 Mar. 2017 | ISBN: 1786468719 | 651 Pages | EPUB/PDF (conv) | 12.4 MB
Key Features
Start with the basics, then enhance your knowledge with in-depth discussions on language features, third-party libraries, design patterns and more
Practical examples that show how to use TypeScript with popular frameworks, including Backbone, Angular 2, React, Aurelia, Node and others
Focus on test-driven development to build high quality applications that are modular, scalable and adaptable
Book Description
The TypeScript language, compiler and open-source development toolset brings JavaScript development up to the enterprise level. It allows us to use ES5, ES6 and ES7 JavaScript language features today - including classes, interfaces, generics, modules and more. It's simple typing syntax enables building large, robust applications using object-oriented techniques and industry standard design principles.
Packed with practical, real-world examples, this book is a guide to bringing the benefits of strongly typed, object-oriented programming and design principles into the JavaScript development space. Starting with core language features, and working through more advanced topics such as generics and asynchronous programming techniques, you will learn how to gain maximum benefit from your JavaScript development with TypeScript. With a strong focus on test-driven development, and coverage of many popular and in-demand JavaScript frameworks, you can fast-track your TypeScript knowledge to a professional level. By the end of this book, you will be able to confidently build TypeScript applications, whether you are targeting Angular 2, Aurelia, React, Backbone, Node or any other JavaScript framework.
What you will learn
Gain an insight into core and advanced TypeScript language features including inheritance, generics, asynchronous programming techniques, promises, decorators and more
Integrate your existing JavaScrip
TypeScript 允许我们遍历某种类型的属性，并通过 keyof 操作符提取其属性的名称。
该操作符可以用于获取某种 类型 的所有键，其返回类型是 联合类型，简单的说，它是作用于类型的，返回类型为联合类型。
将类型对应的对象中的属性解构出来，并作为联合类型返回。
直接作用 interface 类型时， interface 对应的为对象， keyof 将对象中的属性名都结构出来，并作为联合类型返回。
interface IPerson {
  name: string,
				
TypeScript中的运算符与JavaScript中的运算符相同，包括算术运算符（+、-、*、/、%）、比较运算符（>、<、>=、<=、==、!=、===、!==）、逻辑运算符（&&、||、!）、位运算符（&、|、^、~、<<、>>、>>>）等等。
TypeScript还引入了一些新的运算符，其中一个重要的是“?”运算符（也称为“非空断言运算符”），它可以用来断言一个值不为null或undefined。例如：
```typescript
let myString: string | undefined;
// 断言myString不为undefined或null
let myLength: number = myString!.length;
另一个重要的运算符是“as”运算符，用于类型断言。例如：
```typescript
let myObject: any = { name: "John", age: 30 };
// 将myObject转换为Person类型
let myPerson: Person = myObject as Person;
除此之外，TypeScript还支持其他运算符，例如“keyof”运算符用于获取一个类型的所有键名，以及“in”运算符用于判断一个键名是否存在于一个对象中。