1. typescript是什么 #

typescript

2. TypeScript安装和编译 #

2.1 安装 # 

cnpm i typescript -g

tsc helloworld.ts

2.2 Vscode+TypeScript #

2.2.1 生成配置文件 # 

tsc --init

{
  "compilerOptions": {
    /* Basic Options */
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. 指定ECMAScript的目标版本*/
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. 指定模块代码的生成方式*/
    // "lib": [],                             /* Specify library files to be included in the compilation. 指定编译的时候用来包含的编译文件*/
    // "allowJs": true,                       /* Allow javascript files to be compiled. 允许编译JS文件*/
    // "checkJs": true,                       /* Report errors in .js files. 在JS中包括错误*/
    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. 指定JSX代码的生成方式 是保留还是react-native或者react*/
    // "declaration": true,                   /* Generates corresponding '.d.ts' file.生成相应的类型声明文件 */
    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. 为每个类型声明文件生成相应的sourcemap*/
    // "sourceMap": true,                     /* Generates corresponding '.map' file. 生成对应的map文件 */
    // "outFile": "./",                       /* Concatenate and emit output to single file. 合并并且把编译后的内容输出 到一个文件里*/
    // "outDir": "./",                        /* Redirect output structure to the directory.按原始结构输出到目标目录 */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. 指定输入文件的根目录，用--outDir来控制输出的目录结构*/
    // "composite": true,                     /* Enable project compilation 启用项目编译*/
    // "removeComments": true,                /* Do not emit comments to output. 移除注释*/
    // "noEmit": true,                        /* Do not emit outputs. 不要输出*/
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. 当目标是ES5或ES3的时候提供对for-of、扩展运算符和解构赋值中对于迭代器的完整支持*/
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule').r把每一个文件转译成一个单独的模块 */

    /* Strict Type-Checking Options */
    //"strict": true,                           /* Enable all strict type-checking options. 启用完全的严格类型检查 */
    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. 不能使用隐式的any类型*/
    // "strictNullChecks": true,              /* Enable strict null checks. 启用严格的NULL检查*/
    // "strictFunctionTypes": true,           /* Enable strict checking of function types. 启用严格的函数类型检查*/
    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions.启用函数上严格的bind call 和apply方法 */
    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. 启用类上初始化属性检查*/
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type.在默认的any中调用 this表达式报错 */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. 在严格模式下解析并且向每个源文件中发射use strict*/

    /* Additional Checks */
    // "noUnusedLocals": true,                /* Report errors on unused locals. 有未使用到的本地变量时报错 */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. 有未使用到的参数时报错*/
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. 当不是所有的代码路径都有返回值的时候报错*/
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. 在switch表达式中没有替代的case会报错 */

    /* Module Resolution Options */
    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). 指定模块的解析策略 node classic*/
    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. 在解析非绝对路径模块名的时候的基准路径*/
    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. 一些路径的集合*/
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. 根目录的列表，在运行时用来合并内容*/
    // "typeRoots": [],                       /* List of folders to include type definitions from. 用来包含类型声明的文件夹列表*/
    // "types": [],                           /* Type declaration files to be included in compilation.在编译的时候被包含的类型声明 */
    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking.当没有默认导出的时候允许默认导入，这个在代码执行的时候没有作用，只是在类型检查的时候生效 */
    //"esModuleInterop": true                   /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'.*/
    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks.不要symlinks解析的真正路径 */

    /* Source Map Options */
    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. 指定ts文件位置*/
    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. 指定 map文件存放的位置 */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. 源文件和sourcemap 文件在同一文件中，而不是把map文件放在一个单独的文件里*/
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. 源文件和sourcemap 文件在同一文件中*/

    /* Experimental Options */
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. 启动装饰器*/
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
  }
}

2.2.2 执行编译 # 

tsc

2.2.3 vscode运行 #

2.2.4 npm scripts #

2.2.5 npm scripts 的 PATH #

3. 数据类型 #

3.1 布尔类型(boolean) # 

let married: boolean=false;

3.2 数字类型(number) # 

let age: number=10;

3.3 字符串类型(string) # 

let firstname: string='zfpx';

3.4 数组类型(array) # 

let arr2: number[]=[4,5,6];
let arr3: Array<number>=[7,8,9];

3.5 元组类型(tuple) # 

let zhufeng:[string,number] = ['zhufeng',5];
zhufeng[0].length;
zhufeng[1].toFixed(2);
元组 数组
每一项可以是不同的类型 每一项都是同一种类型
有预定义的长度 没有长度限制
用于表示一个固定的结构 用于表示一个列表 
const animal:[string,number,boolean] = ['zhufeng',10,true];

3.6 枚举类型(enum) #

3.6.1 普通枚举 # 

enum Gender{
    GIRL,
    BOY
}
console.log(`李雷是${Gender.BOY}`);
console.log(`韩梅梅是${Gender.GIRL}`);

enum Week{
    MONDAY=1,
    TUESDAY=2
}
console.log(`今天是星期${Week.MONDAY}`);

3.6.2 常数枚举 # 

const enum Colors {
    Red,
    Yellow,
    Blue
}

let myColors = [Colors.Red, Colors.Yellow, Colors.Blue];

const enum Color {Red, Yellow, Blue = "blue".length};

3.7 任意类型(any) # 

let root:any=document.getElementById('root');
root.style.color='red';

let root:(HTMLElement|null)=document.getElementById('root');
root!.style.color='red';//非空断言操作符

3.8 null 和 undefined # 

let x: number;
x = 1;
x = undefined;    
x = null;   

let y: number | null | undefined;
y = 1;
y = undefined;   
y = null;

3.9 void 类型 # 

function greeting(name:string):void {
    console.log('hello',name);
    //当我们声明一个变量类型是 void 的时候，它的非严格模式(strictNullChecks:false)下仅可以被赋值为 null 和 undefined
    //严格模式(strictNullChecks:true)下只能返回undefined
    //return null;
    //return undefined;
}

3.10 never类型 #

never是其它类型(null undefined)的子类型，代表不会出现的值

3.10.1 # 

// 返回never的函数 必须存在 无法达到（ unreachable ） 的终点
function error(message: string): never {
    throw new Error(message);
}
let result1 = error('hello');
// 由类型推论得到返回值为 never
function fail() {
    return error("Something failed");
}
let result = fail();

// 返回never的函数 必须存在 无法达到（ unreachable ） 的终点
function infiniteLoop(): never {
    while (true) {}
}

3.10.2 strictNullChecks # 

// Compiled with --strictNullChecks
function fn(x: number | string) {
  if (typeof x === 'number') {
    // x: number 类型
  } else if (typeof x === 'string') {
    // x: string 类型
  } else {
    // x: never 类型
    // --strictNullChecks 模式下，这里的代码将不会被执行，x 无法被观察
  }
}

3.10.3 never 和 void 的区别 #

3.11 Symbol # 

const sym1 = Symbol('key');
const sym2 = Symbol('key');
Symbol('key') === Symbol('key') // false

3.12 BigInt # 

const max = Number.MAX_SAFE_INTEGER;// 2**53-1
console.log(max + 1 === max + 2);

const max = BigInt(Number.MAX_SAFE_INTEGER);
console.log(max + 1n === max + 2n);

let foo: number;
let bar: bigint;
foo =bar;
bar = foo;

3.13 类型推论 # 

let username2;
username2 = 10;
username2 = 'zhufeng';
username2 = null;

3.14 包装对象（Wrapper Object） # 

let name = 'zhufeng';
console.log(name.toUpperCase());

console.log((new String('zhufeng')).toUpperCase());

let isOK: boolean = true; // 编译通过
let isOK: boolean = Boolean(1) // 编译通过
let isOK: boolean = new Boolean(1); // 编译失败   期望的 isOK 是一个原始数据类型

3.15 联合类型 # 

let name: string | number;
console.log(name.toString());
name = 3;
console.log(name.toFixed(2));
name = 'zhufeng';
console.log(name.length);

export {};

3.16 类型断言 # 

let name: string | number;
console.log((name as string).length);
console.log((name as number).toFixed(2));
console.log((name as boolean));

双重断言

interface Person {
    name: string;
    age: number;
}
const person = 'zhufeng' as any as Person; // ok

3.17 字面量类型和类型字面量 # 

const up:'Up'= 'Up';
const down: "Down" = "Down";
const left: "Left" = "Left";
const right: "Right" = "Right";
type Direction = 'Up' | 'Down' | 'Left' | 'Right';
function move(direction: Direction) {}
move("Up");

type Person = {
  name:string,
  age:number
};

3.18 字符串字面量 vs 联合类型 #

4. 函数 #

4.1 函数的定义 # 

function hello(name:string):void {
    console.log('hello',name);
}
hello('zfpx');

4.2 函数表达式 # 

type GetUsernameFunction = (x:string,y:string)=>string;
let getUsername:GetUsernameFunction = function(firstName,lastName){
  return firstName + lastName;
}

4.3 没有返回值 # 

let hello2 = function (name:string):void {
    console.log('hello2',name);
    return undefined;
}
hello2('zhufeng');

4.4 可选参数 #

在TS中函数的形参和实参必须一样，不一样就要配置可选参数,而且必须是最后一个参数

function print(name:string,age?:number):void {
    console.log(name,age);
}
print('zfpx');

4.5 默认参数 # 

function ajax(url:string,method:string='GET') {
    console.log(url,method);
}
ajax('/users');

4.6 剩余参数 # 

function sum(...numbers:number[]) {
    return numbers.reduce((val,item)=>val+=item,0);
}
console.log(sum(1,2,3));

4.7 函数重载 # 

let obj: any={};
function attr(val: string): void;
function attr(val: number): void;
function attr(val:any):void {
    if (typeof val === 'string') {
        obj.name=val;
    } else {
        obj.age=val;
    }
}
attr('zfpx');
attr(9);
attr(true);
console.log(obj);

5. 类 #

5.1 如何定义类 # 

class Person{
    name:string;
    getName():void{
        console.log(this.name);
    }
}
let p1 = new Person();
p1.name = 'zhufeng';
p1.getName();

/**
 * 当我们写一个类的时候,会得到2个类型
 * 1. 构造函数类型的函数类型
 * 2. 类的实例类型
 */
class Component {
    static myName: string = '静态名称属性';
    myName: string = '实例名称属性';
}
let com = Component;
//Component类名本身表示的是实例的类型
//ts 一个类型 一个叫值 
//冒号后面的是类型
//放在=后面的是值
let c: Component = new Component();
let f: typeof Component = com;

5.2 存取器 # 

class User {
    myname:string;
    constructor(myname: string) {
        this.myname = myname;
    }
    get name() {
        return this.myname;
    }
    set name(value) {
        this.myname = value;
    }
}

let user = new User('zhufeng');
user.name = 'jiagou'; 
console.log(user.name); 

"use strict";
var User = /** @class */ (function () {
    function User(myname) {
        this.myname = myname;
    }
    Object.defineProperty(User.prototype, "name", {
        get: function () {
            return this.myname;
        },
        set: function (value) {
            this.myname = value;
        },
        enumerable: true,
        configurable: true
    });
    return User;
}());
var user = new User('zhufeng');
user.name = 'jiagou';
console.log(user.name);

5.3 参数属性 # 

class User {
    constructor(public myname: string) {}
    get name() {
        return this.myname;
    }
    set name(value) {
        this.myname = value;
    }
}

let user = new User('zhufeng');
console.log(user.name); 
user.name = 'jiagou'; 
console.log(user.name);

5.4 readonly # 

class Animal {
    public readonly name: string
    constructor(name:string) {
        this.name = name;
    }
    changeName(name:string){
        this.name = name;
    }
}

let a = new Animal('zhufeng');
a.changeName('jiagou');

5.5 继承 # 

class Person {
    name: string;//定义实例的属性，默认省略public修饰符
    age: number;
    constructor(name:string,age:number) {//构造函数
        this.name=name;
        this.age=age;
    }
    getName():string {
        return this.name;
    }
    setName(name:string): void{
        this.name=name;
    }
}
class Student extends Person{
    no: number;
    constructor(name:string,age:number,no:number) {
        super(name,age);
        this.no=no;
    }
    getNo():number {
        return this.no;
    }
}
let s1=new Student('zfpx',10,1);
console.log(s1);

5.6 类里面的修饰符 # 

class Father {
    public name: string;  //类里面 子类 其它任何地方外边都可以访问
    protected age: number; //类里面 子类 都可以访问,其它任何地方不能访问
    private money: number; //类里面可以访问， 子类和其它任何地方都不可以访问
    constructor(name:string,age:number,money:number) {//构造函数
        this.name=name;
        this.age=age;
        this.money=money;
    }
    getName():string {
        return this.name;
    }
    setName(name:string): void{
        this.name=name;
    }
}
class Child extends Father{
    constructor(name:string,age:number,money:number) {
        super(name,age,money);
    }
    desc() {
        console.log(`${this.name} ${this.age} ${this.money}`);
    }
}

let child = new Child('zfpx',10,1000);
console.log(child.name);
console.log(child.age);
console.log(child.money);

5.7 静态属性 静态方法 # 

class Father {
    static className='Father';
    static getClassName() {
        return Father.className;
    }
    public name: string;
    constructor(name:string) {//构造函数
        this.name=name;
    }

}
console.log(Father.className);
console.log(Father.getClassName());

5.8 装饰器 # 

class Person{
    say() {
        console.log('hello')
    }
}

function Person() {}
Object.defineProperty(Person.prototype, 'say', {
    value: function() { console.log('hello'); },
    enumerable: false,
    configurable: true,
    writable: true
});

5.8.1 类装饰器 # 

namespace a {
    //当装饰器作为修饰类的时候，会把构造器传递进去
    function addNameEat(constructor: Function) {
      constructor.prototype.name = "zhufeng";
      constructor.prototype.eat = function () {
        console.log("eat");
      };
    }
    @addNameEat
    class Person {
      name!: string;
      eat!: Function;
      constructor() {}
    }
    let p: Person = new Person();
    console.log(p.name);
    p.eat();
}

namespace b {
    //还可以使用装饰器工厂
    function addNameEatFactory(name:string) {
    return function (constructor: Function) {
        constructor.prototype.name = name;
        constructor.prototype.eat = function () {
        console.log("eat");
        };
    };
    }
    @addNameEatFactory('zhufeng')
    class Person {
      name!: string;
      eat!: Function;
      constructor() {}}
    let p: Person = new Person();
    console.log(p.name);
    p.eat();
}

namespace c {
    //还可以替换类,不过替换的类要与原类结构相同
    function enhancer(constructor: Function) {
    return class {
        name: string = "jiagou";
        eat() {
        console.log("吃饭饭");
        }
    };
    }
    @enhancer
    class Person {
      name!: string;
      eat!: Function;
      constructor() {}}
    let p: Person = new Person();
    console.log(p.name);
    p.eat();

}

5.8.2 属性装饰器 # 

namespace d {
    //修饰实例属性
    function upperCase(target: any, propertyKey: string) {
        let value = target[propertyKey];
        const getter = function () {
            return value;
        }
        // 用来替换的setter
        const setter = function (newVal: string) {
            value = newVal.toUpperCase()
        };
        // 替换属性，先删除原先的属性，再重新定义属性
        if (delete target[propertyKey]) {
            Object.defineProperty(target, propertyKey, {
                get: getter,
                set: setter,
                enumerable: true,
                configurable: true
            });
        }
    }
    //修饰实例方法
    function noEnumerable(target: any, property: string, descriptor: PropertyDescriptor) {
        console.log('target.getName', target.getName);
        console.log('target.getAge', target.getAge);
        descriptor.enumerable = true;
    }
    //重写方法
    function toNumber(target: any, methodName: string, descriptor: PropertyDescriptor) {
        let oldMethod = descriptor.value;
        descriptor.value = function (...args: any[]) {
            args = args.map(item => parseFloat(item));
            return oldMethod.apply(this, args);
        }
    }
    class Person {
        @upperCase
        name: string = 'zhufeng'
        public static age: number = 10
        constructor() { }
        @noEnumerable
        getName() {
            console.log(this.name);
        }
        @toNumber
        sum(...args: any[]) {
            return args.reduce((accu: number, item: number) => accu + item, 0);
        }
    }
    let p: Person = new Person();
    for (let attr in p) {
        console.log('attr=', attr);
    }
    p.name = 'jiagou';
    p.getName();
    console.log(p.sum("1", "2", "3"));
}

5.8.3 参数装饰器 # 

namespace d {
    interface Person {
        age: number;
    }
    function addAge(target: any, methodName: string, paramsIndex: number) {
        console.log(target);
        console.log(methodName);
        console.log(paramsIndex);
        target.age = 10;
    }
    class Person {
        login(username: string, @addAge password: string) {
            console.log(this.age, username, password);
        }
    }
    let p = new Person();
    p.login('zhufeng', '123456')
}

5.8.4 装饰器执行顺序 # 

namespace e {
    function Class1Decorator() {
        return function (target: any) {
            console.log("类1装饰器");
        }
    }
    function Class2Decorator() {
        return function (target: any) {
            console.log("类2装饰器");
        }
    }
    function MethodDecorator() {
        return function (target: any, methodName: string, descriptor: PropertyDescriptor) {
            console.log("方法装饰器");
        }
    }
    function Param1Decorator() {
        return function (target: any, methodName: string, paramIndex: number) {
            console.log("参数1装饰器");
        }
    }
    function Param2Decorator() {
        return function (target: any, methodName: string, paramIndex: number) {
            console.log("参数2装饰器");
        }
    }
    function PropertyDecorator(name: string) {
        return function (target: any, propertyName: string) {
            console.log(name + "属性装饰器");
        }
    }

    @Class1Decorator()
    @Class2Decorator()
    class Person {
        @PropertyDecorator('name')
        name: string = 'zhufeng';
        @PropertyDecorator('age')
        age: number = 10;
        @MethodDecorator()
        greet(@Param1Decorator() p1: string, @Param2Decorator() p2: string) { }
    }
}
/**
name属性装饰器
age属性装饰器
参数2装饰器
参数1装饰器
方法装饰器
类2装饰器
类1装饰器
 */

5.9 抽象类 # 

abstract class Animal {
    name!:string;
    abstract speak():void;
}
class Cat extends Animal{
    speak(){
        console.log('喵喵喵');
    }
}
let animal = new Animal();//Cannot create an instance of an abstract class
animal.speak();
let cat = new Cat();
cat.speak();
访问控制修饰符 private protected public
只读属性 readonly
静态属性 static
抽象类、抽象方法 abstract

5.10 抽象方法 # 

abstract class Animal{
    abstract speak():void;
}
class Dog extends  Animal{
    speak(){
        console.log('小狗汪汪汪');
    }
}
class Cat extends  Animal{
    speak(){
        console.log('小猫喵喵喵');
    }
}
let dog=new Dog();
let cat=new Cat();
dog.speak();
cat.speak();

5.11 重写(override) vs 重载(overload) # 

class Animal{
    speak(word:string):string{
        return '动作叫:'+word;
    }
}
class Cat extends Animal{
    speak(word:string):string{
        return '猫叫:'+word;
    }
}
let cat = new Cat();
console.log(cat.speak('hello'));
//--------------------------------------------
function double(val:number):number
function double(val:string):string
function double(val:any):any{
  if(typeof val == 'number'){
    return val *2;
  }
  return val + val;
}

let r = double(1);
console.log(r);

5.12 继承 vs 多态 # 

class Animal{
    speak(word:string):string{
        return 'Animal: '+word;
    }
}
class Cat extends Animal{
    speak(word:string):string{
        return 'Cat:'+word;
    }
}
class Dog extends Animal{
    speak(word:string):string{
        return 'Dog:'+word;
    }
}
let cat = new Cat();
console.log(cat.speak('hello'));
let dog = new Dog();
console.log(dog.speak('hello'));

6. 接口 #

6.1 接口 #

6.1.1 对象的形状 # 

//接口可以用来描述`对象的形状`,少属性或者多属性都会报错
interface Speakable{
    speak():void;
    name?:string;//？表示可选属性
}

let speakman:Speakable = {
    speak(){},//少属性会报错
    name,
    age//多属性也会报错
}

6.1.2 行为的抽象 # 

//接口可以在面向对象编程中表示为行为的抽象
interface Speakable{
    speak():void;
}
interface Eatable{
    eat():void
}
//一个类可以实现多个接口
class Person implements Speakable,Eatable{
    speak(){
        console.log('Person说话');
    }
    eat(){}
}
class TangDuck implements Speakable{
    speak(){
        console.log('TangDuck说话');
    }
    eat(){}
}

6.1.3 任意属性 # 

//无法预先知道有哪些新的属性的时候,可以使用 `[propName:string]:any`,propName名字是任意的
interface Person {
  readonly id: number;
  name: string;
  [propName: string]: any;
}

let p1 = {
  id:1,
  name:'zhufeng',
  age:10
}

6.2 接口的继承 # 

interface Speakable {
    speak(): void
}
interface SpeakChinese extends Speakable {
    speakChinese(): void
}
class Person implements SpeakChinese {
    speak() {
        console.log('Person')
    }
    speakChinese() {
        console.log('speakChinese')
    }
}

6.3 readonly # 

interface Person{
  readonly id:number;
  name:string
}
let tom:Person = {
  id :1,
  name:'zhufeng'
}
tom.id = 1;

6.4 函数类型接口 # 

interface discount{
  (price:number):number
}
let cost:discount = function(price:number):number{
   return price * .8;
}

6.5 可索引接口 # 

interface UserInterface {
  [index:number]:string
}
let arr:UserInterface = ['zfpx1','zfpx2'];
console.log(arr);

interface UserInterface2 {
  [index:string]:string
}
let obj:UserInterface2 = {name:'zhufeng'};

6.6 类接口 # 

interface Speakable {
    name: string;
    speak(words: string): void
}
class Dog implements Speakable {
    name!: string;
    speak(words:string) {
        console.log(words);
    }
}
let dog = new Dog();
dog.speak('汪汪汪');

6.7 构造函数的类型 # 

class Animal{
  constructor(public name:string){
  }
}
//不加new是修饰函数的,加new是修饰类的
interface WithNameClass{
  new(name:string):Animal
}
function createAnimal(clazz:WithNameClass,name:string){
   return new clazz(name);
}
let a = createAnimal(Animal,'zhufeng');
console.log(a.name);

6.8 抽象类 vs 接口 # 

abstract class Animal{
    name:string;
    constructor(name:string){
      this.name = name;
    }
    abstract speak():void;
  }
interface Flying{
      fly():void
}
class Duck extends Animal implements Flying{
      speak(){
          console.log('汪汪汪');
      }
      fly(){
          console.log('我会飞');
      }
}
let duck = new Duck('zhufeng');
duck.speak();
duck.fly();

7. 泛型 #

7.1 泛型函数 # 

function createArray(length: number, value: any): Array<any> {
  let result: any = [];
  for (let i = 0; i < length; i++) {
    result[i] = value;
  }
  return result;
}
let result = createArray(3,'x');
console.log(result);

使用了泛型

function createArray<T>(length: number, value: T): Array<T> {
    let result: T[] = [];
    for (let i = 0; i < length; i++) {
      result[i] = value;
    }
    return result;
  }
let result = createArray2<string>(3,'x');
console.log(result);

7.2 类数组 # 

function sum() {
    let args: IArguments = arguments;
    for (let i = 0; i < args.length; i++) {
        console.log(args[i]);
    }
}
sum(1, 2, 3);

let root = document.getElementById('root');
let children: HTMLCollection = (root as HTMLElement).children;
children.length;
let nodeList: NodeList = (root as HTMLElement).childNodes;
nodeList.length;

7.3 泛型类 #

7.3.1 泛型类 # 

class MyArray<T>{
    private list:T[]=[];
    add(value:T) {
        this.list.push(value);
    }
    getMax():T {
        let result=this.list[0];
        for (let i=0;i<this.list.length;i++){
            if (this.list[i]>result) {
                result=this.list[i];
            }
        }
        return result;
    }
}
let arr=new MyArray();
arr.add(1); arr.add(2); arr.add(3);
let ret = arr.getMax();
console.log(ret);

7.3.2 泛型与 new # 

function factory<T>(type: {new():T}): T {
  return new type(); // This expression is not constructable.
}

7.5 泛型接口 # 

interface Calculate{
  <T>(a:T,b:T):T
}
let add:Calculate = function<T>(a:T,b:T){
  return a;
}
add<number>(1,2);

7.6 多个类型参数 # 

function swap<A,B>(tuple:[A,B]):[B,A]{
  return [tuple[1],tuple[0]];
}
let swapped = swap<string,number>(['a',1]);
console.log(swapped);
console.log(swapped[0].toFixed(2));
console.log(swapped[1].length);

7.7 默认泛型类型 # 

function createArray3<T=number>(length: number, value: T): Array<T> {
  let result: T[] = [];
  for (let i = 0; i < length; i++) {
    result[i] = value;
  }
  return result;
}
let result2 = createArray3(3,'x');
console.log(result2);

7.8 泛型约束 # 

function logger<T>(val: T) {
    console.log(val.length); //直接访问会报错
}
//可以让泛型继承一个接口
interface LengthWise {
    length: number
}
//可以让泛型继承一个接口
function logger2<T extends LengthWise>(val: T) {
    console.log(val.length)
}
logger2('zhufeng');
logger2(1);

7.9 泛型接口 # 

interface Cart<T>{
  list:T[]
}
let cart:Cart<{name:string,price:number}> = {
  list:[{name:'zhufeng',price:10}]
}
console.log(cart.list[0].name,cart.list[0].price);

7.10 compose #

compose

import compose from ".";
/* zero functions */
console.log(compose()<string>("zhufeng"));
/* one functions */
interface F{
    (a:string):string
}
let f: F = (a:string):string=>a+'f';
console.log(compose<F>(f)("zhufeng"));
/* two functions */
type A = string;
type R = string;
type T = string[];

let f1 = (a: A): R => a + "f1";
let f2 = (...a: T): A => a + "f2";
console.log(compose<A,T,R>(f1,f2)("zhufeng"));

7.11 泛型类型别名 # 

type Cart<T> = {list:T[]} | T[];
let c1:Cart<string> = {list:['1']};
let c2:Cart<number> = [1];

7.12 泛型接口 vs 泛型类型别名 #

8.结构类型系统 #

8.1 接口的兼容性 # 

interface Animal {
    name: string;
    age: number;
}

interface Person {
    name: string;
    age: number;
    gender: number
}
// 要判断目标类型`Person`是否能够兼容输入的源类型`Animal`
function getName(animal: Animal): string {
    return animal.name;
}

let p = {
    name: 'zhufeng',
    age: 10,
    gender: 0
}

getName(p);
//只有在传参的时候两个变量之间才会进行兼容性的比较，赋值的时候并不会比较,会直接报错
let a: Animal = {
    name: 'zhufeng',
    age: 10,
    gender: 0
}

8.2 基本类型的兼容性 # 

//基本数据类型也有兼容性判断
let num : string|number;
let str:string='zhufeng';
num = str;

//只要有toString()方法就可以赋给字符串变量
let num2 : {
  toString():string
}

let str2:string='jiagou';
num2 = str2;

8.3 类的兼容性 # 

class Animal{
    name:string
}
class Bird extends Animal{
   swing:number
}

let a:Animal;
a = new Bird();

let b:Bird;
//并不是父类兼容子类，子类不兼容父类
b = new Animal();


class Animal{
  name:string
}
//如果父类和子类结构一样，也可以的
class Bird extends Animal{}

let a:Animal;
a = new Bird();

let b:Bird;
b = new Animal();


//甚至没有关系的两个类的实例也是可以的
class Animal{
  name:string
}
class Bird{
  name:string
}
let a:Animal ;
a = new Bird();
let b:Bird;
b = new Animal();

8.4 函数的兼容性 #

8.4.1 比较参数 # 

type sumFunc = (a:number,b:number)=>number;
let sum:sumFunc;
function f1(a:number,b:number):number{
  return a+b;
}
sum = f1;

//可以省略一个参数
function f2(a:number):number{
   return a;
}
sum = f2;

//可以省略二个参数
function f3():number{
    return 0;
}
sum = f3;

 //多一个参数可不行
function f4(a:number,b:number,c:number){
    return a+b+c;
}
sum = f4;

8.4.2 比较返回值 # 

type GetPerson = ()=>{name:string,age:number};
let getPerson:GetPerson;
//返回值一样可以
function g1(){
    return {name:'zhufeng',age:10};
}
getPerson = g1;
//返回值多一个属性也可以
function g2(){
    return {name:'zhufeng',age:10,gender:'male'};
}
getPerson = g2;
//返回值少一个属性可不行
function g3(){
    return {name:'zhufeng'};
}
getPerson = g3;
//因为有可能要调用返回值上的方法
getPerson().age.toFixed();

8.5 函数的协变与逆变 # 

class Animal{}
class Dog extends Animal{
    public name:string = 'Dog'
}
class BlackDog extends Dog {
    public age: number = 10
}
class WhiteDog extends Dog {
    public home: string = '北京'
}
let animal: Animal;
let blackDog: BlackDog;
let whiteDog: WhiteDog;
type Callback = (dog: Dog)=>Dog;
function exec(callback:Callback):void{
    callback(whiteDog);
}
//不行  callback(redDog);
type ChildToChild = (blackDog: BlackDog) => BlackDog;
const childToChild: ChildToChild = (blackDog: BlackDog): BlackDog => blackDog
exec(childToChild);

//也不行,理由同上
type ChildToParent = (blackDog: BlackDog) => Animal;
const childToParent: ChildToParent = (blackDog: BlackDog): Animal => animal
exec(childToParent);

//不行 因为有可能调用返回的Dog的方法
type ParentToParent = (animal: Animal) => Animal;
const parentToParent: ParentToParent = (animal: Animal): Animal => animal
exec(parentToParent);

//可以,所有的狗都是动物,返回的不管什么狗都是狗
type ParentToChild = (animal: Animal) => BlackDog;
const parentToChild: ParentToChild = (animal: Animal): BlackDog => blackDog
exec(parentToChild);
//(Animal → Greyhound) ≼ (Dog → Dog)
//返回值类型很容易理解：黑狗是狗的子类。但参数类型则是相反的：动物是狗的父类！

// string | number|boolean 是 string | number的父类型
// string是string|number的子类型
type Callback2 = (a: string | number) => string | number;
function exec2(callback: Callback2):void{
    callback('');
}
type ParentToChild2 = (a: string | number | boolean) => string;
const parentToChild2: ParentToChild2 = (a: string | number | boolean): string => ''
exec2(parentToChild2);

type Callback3 = (a: string | number) => string | number;
function exec3(callback: Callback2): void {
    callback('');
}
type ParentToParent3 = (a: string) => string;
const parentToParent3: ParentToParent3 = (a: string): string => ''
exec3(parentToChild3);

8.6 泛型的兼容性 # 

//接口内容为空没用到泛型的时候是可以的
//1.接口内容为空没用到泛型的时候是可以的
interface Empty<T>{}
let x!:Empty<string>;
let y!:Empty<number>;
x = y;

//2.接口内容不为空的时候不可以
interface NotEmpty<T>{
  data:T
}
let x1!:NotEmpty<string>;
let y1!:NotEmpty<number>;
x1 = y1;

//实现原理如下,称判断具体的类型再判断兼容性
interface NotEmptyString{
    data:string
}

interface NotEmptyNumber{
    data:number
}
let xx2!:NotEmptyString;
let yy2!:NotEmptyNumber;
xx2 = yy2;

8.7 枚举的兼容性 # 

//数字可以赋给枚举
enum Colors {Red,Yellow}
let c:Colors;
c = Colors.Red;
c = 1;
c = '1';

//枚举值可以赋给数字
let n:number;
n = 1;
n = Colors.Red;

9.类型保护 #

9.1 typeof 类型保护 # 

function double(input: string | number | boolean) {
    if (typeof input === 'string') {
        return input + input;
    } else {
        if (typeof input === 'number') {
            return input * 2;
        } else {
            return !input;
        }
    }
}

9.2 instanceof类型保护 # 

class Animal {
    name!: string;
}
class Bird extends Animal {
    swing!: number
}
function getName(animal: Animal) {
    if (animal instanceof Bird) {
        console.log(animal.swing);
    } else {
        console.log(animal.name);
    }
}

9.3 null保护 # 

function getFirstLetter(s: string | null) {
    //第一种方式是加上null判断
    if (s == null) {
        return '';
    }
    //第二种处理是增加一个或的处理
    s = s || '';
    return s.charAt(0);
}
//它并不能处理一些复杂的判断，需要加非空断言操作符
function getFirstLetter2(s: string | null) {
    function log() {
        console.log(s!.trim());
    }
    s = s || '';
    log();
    return s.charAt(0);
}

9.4 链判断运算符 # 

a?.b; //如果a是null/undefined,那么返回undefined，否则返回a.b的值.
a == null ? undefined : a.b;

a?.[x]; //如果a是null/undefined,那么返回undefined，否则返回a[x]的值
a == null ? undefined : a[x];

a?.b(); // 如果a是null/undefined,那么返回undefined
a == null ? undefined : a.b(); //如果a.b不函数的话抛类型错误异常,否则计算a.b()的结果

a?.(); //如果a是null/undefined,那么返回undefined
a == null ? undefined : a(); //如果A不是函数会抛出类型错误
//否则 调用a这个函数

链判断运算符 还处于 stage1 阶段,TS 也暂时不支持

9.5 可辨识的联合类型 # 

interface WarningButton{
  class:'warning',
  text1:'修改'
}
interface DangerButton{
  class:'danger',
  text2:'删除'
}
type Button = WarningButton|DangerButton;
function getButton(button:Button){
 if(button.class=='warning'){
  console.log(button.text1);
 }
 if(button.class=='danger'){
  console.log(button.text2);
 }
}

类型字面量+可辨识联合类型

interface User {
    username: string
}
type Action = {
    type:'add',
    payload:User
} | {
    type: 'delete'
    payload: number
}
const UserReducer = (action: Action) => {
  switch (action.type) {
    case "add":
      let user: User = action.payload;
      break;
    case "delete":
      let id: number = action.payload;
      break;
    default:
      break;
  }
};

9.6 in操作符 # 

interface Bird {
    swing: number;
}

interface Dog {
    leg: number;
}

function getNumber(x: Bird | Dog) {
    if ("swing" in x) {
      return x.swing;
    }
    return x.leg;
}

9.7 自定义的类型保护 # 

function isType1(type: Type1Class | Type2Class): type is Type1Class {
    return (<Type1Class>type).func1 !== undefined;
}

interface Bird {
  swing: number;
}

interface Dog {
  leg: number;
}

//没有相同字段可以定义一个类型保护函数
function isBird(x:Bird|Dog): x is Bird{
  return (<Bird>x).swing == 2;
  //return (x as Bird).swing == 2;
}

function getAnimal(x: Bird | Dog) {
  if (isBird(x)) {
    return x.swing;
  }
  return x.leg;
}

9.8 unknown #

9.8.1 any 类型 # 

let value: any;

value = true;             // OK
value = 42;               // OK
value = "Hello World";    // OK
value = [];               // OK
value = {};               // OK
value = Math.random;      // OK
value = null;             // OK
value = undefined;        // OK


let value: any;
value.foo.bar;  // OK
value.trim();   // OK
value();        // OK
new value();    // OK

9.8.2 unknown 类型 # 


let value: unknown;

value = true;             // OK
value = 42;               // OK
value = "Hello World";    // OK
value = [];               // OK
value = {};               // OK
value = Math.random;      // OK
value = null;             // OK
value = undefined;        // OK
value = new TypeError();  // OK


let value: unknown;
let value1: unknown = value;   // OK
let value2: any = value;       // OK
let value3: boolean = value;   // Error
let value4: number = value;    // Error
let value5: string = value;    // Error
let value6: object = value;    // Error
let value7: any[] = value;     // Error
let value8: Function = value;  // Error

9.8.3 缩小 unknown 类型范围 # 

const value: unknown = "Hello World";
const someString: string = value as string;

9.8.4 联合类型中的 unknown 类型 #

9.8.5 交叉类型中的 unknown 类型 # 

type IntersectionType1 = unknown & null;       // null
type IntersectionType2 = unknown & undefined;  // undefined
type IntersectionType3 = unknown & string;     // string
type IntersectionType4 = unknown & number[];   // number[]
type IntersectionType5 = unknown & any;        // any

9.8.6 never是unknown的子类型 # 

type isNever = never extends unknown ? true : false;

9.8.7 keyof unknown 等于never # 

type key = keyof unknown;

9.8.8 只能对unknown进行等或不等操作，不能进行其它操作 # 

un1===un2;
un1!==un2;
un1 += un2;

9.8.9 不能做任何操作 # 

un.name
un();
new un();

9.8.10 映射属性 #

10. 类型变换 #

10.1 类型推断 #

10.1.1 从右向左 # 

let foo = 1; // foo 是 'number'
let bar = 'zhufeng'; // bar 是 'string'
//foo = bar; // Error: 不能将 'string' 赋值给 `number`

10.1.2 底部流出 # 

function add(a: number, b: number) {
    return a + b;
}
let c = add(1,2);

10.1.3 从左向右 # 

type Sum = (a: number, b: number) => number;
let sum: Sum = (a, b) => {
    a='zhufeng';
    return a + b;
};

10.1.4 结构化 # 

const person = {
    name: 'zhufeng',
    age: 11
};
let name =person.name;
let age =person.age;
age = 'hello'; // Error：不能把 'string' 类型赋值给 'number' 类型

10.1.5 解构 # 

const person = {
    name: 'zhufeng',
    age: 11
};
let { name,age } = person;

age = 'hello'; // Error：不能把 'string' 类型赋值给 'number' 类型

//数组也一样
const numbers = [1, 2, 3];
numbers[0] = 'hello'; // Error：不能把 'string' 类型赋值给 'number' 类型

10.1.5 DefaultProps # 


interface DefaultProps{
    name?:string;
    age?:number;
}
let defaultProps: DefaultProps = {
   name:'zhufeng',
   age:10
}

let props = {
    ...defaultProps,
    home:'北京'
}
type Props = typeof props;

10.1.6 小心使用返回值 # 

function addOne(a:any) {
    return a + 1;
}
function sum(a: number, b: number) {
    return a + addOne(b);
}

type Ret = ReturnType<typeof sum>;

10.1 交叉类型 # 

//TypeScript 交叉类型是将多个类型合并为一个类型
//这让我们可以把现有的多种类型叠加到一起成为一种类型
//它包含了所需的所有类型的特性

export {}
//接口的交叉
interface Bird {
    name: string,
    fly(): void
}
interface Person {
    name: string,
    talk(): void
}
type BirdPerson = Bird & Person;
let p: BirdPerson = { name: 'zhufeng', fly() { }, talk() { } };
p.fly;
p.name
p.talk;

interface X {
    a: string;
    b: string;
}

interface Y {
    a: number;
    c: string
}

type XY = X & Y;
type YX = Y & X;
//c = string & number
//let p1: XY={a:'',b:'',c:''};

联合类型的交叉类型

type Ta = string | number;
type Tb = number | boolean;
type Tc = Ta & Tb;

mixin混入模式可以让你从两个对象中创建一个新对象，新对象会拥有着两个对象所有的功能

interface AnyObject {
    [prop: string]: any;
}

function mixin<T extends AnyObject, U extends AnyObject>(one: T,two: U): T & U {
    const result = <T & U>{};
    for (let key in one) {
        (<T>result)[key] = one[key];
    }
    for (let key in two) {
        (<U>result)[key] = two[key];
    }
    return result;
}

const x = mixin({ name: "zhufeng" }, { age: 11 });
console.log(x.name, x.age);

10.2 typeof # 

//先定义类型，再定义变量
type People = {
    name:string,
    age:number,
    gender:string
}
let p1:People = {
    name:'zhufeng',
    age:10,
    gender:'male'
}

//先定义变量，再定义类型
let p1 = {
    name:'zhufeng',
    age:10,
    gender:'male'
}
type People = typeof p1;
function getName(p:People):string{
    return p.name;
}
getName(p1);

10.3 索引访问操作符 # 

interface Person{
    name:string;
    age:number;
    job:{
        name:string
    };
    interests:{name:string,level:number}[]
}
let FrontEndJob:Person['job'] = {
    name:'前端工程师'
}
let interestLevel:Person['interests'][0]['level'] = 2;

10.4 keyof # 

interface Person{
  name:string;
  age:number;
  gender:'male'|'female';
}
//type PersonKey = 'name'|'age'|'gender';
type PersonKey = keyof Person;

function getValueByKey(p:Person,key:PersonKey){
  return p[key];
}
let val = getValueByKey({name:'zhufeng',age:10,gender:'male'},'name');
console.log(val);

10.5 映射类型 # 

interface Person{
  name:string;
  age:number;
  gender:'male'|'female';
}
//批量把一个接口中的属性都变成可选的
type PartPerson = {
  [Key in keyof Person]?:Person[Key]
}

let p1:PartPerson={};
//也可以使用泛型
type Part<T> = {
  [key in keyof T]?:T[key]
}
let p2:Part<Person>={};

10.6 条件类型 #

10.6.1 定义条件类型 # 

interface Fish {
    name: string
}
interface Water {
    name: string
}
interface Bird {
    name: string
}
interface Sky {
    name: string
}
//若 T 能够赋值给 Fish，那么类型是 Water,否则为 Sky
type Condition<T> = T extends Fish ? Water : Sky;
let condition: Condition<Fish> = { name: '水' };

10.6.2 条件类型的分发 # 

interface Fish {
    fish: string
}
interface Water {
    water: string
}
interface Bird {
    bird: string
}
interface Sky {
    sky: string
}
//naked type
type Condition<T> = T extends Fish ? Water : Sky;

//(Fish extends Fish ? Water : Sky) | (Bird extends Fish ? Water : Sky)
// Water|Sky
let condition1: Condition<Fish | Bird> = { water: '水' };
let condition2: Condition<Fish | Bird> = { sky: '天空' };

//none naked type
//type Condition<T> = [T] extends [Fish] ? Water : Sky;

//never会被自动过滤
type Diff<T, U> = T extends U ? never : T;

type R = Diff<"a" | "b" | "c" | "d", "a" | "c" | "f">;  // "b" | "d"

type Filter<T, U> = T extends U ? T : never;
type R1 = Filter<string | number | boolean, number>;

10.6.3 内置条件类型 #

10.6.3.1 Exclude # 
type Exclude<T, U> = T extends U ? never : T;

type  E = Exclude<string|number,string>;
let e:E = 10;
10.6.3.2 Extract # 
type Extract<T, U> = T extends U ? T : never;

type  E = Extract<string|number,string>;
let e:E = '1';
10.6.3.3 NonNullable # 
type NonNullable<T> = T extends null | undefined ? never : T;

type  E = NonNullable<string|number|null|undefined>;
let e:E = null;
10.6.3.4 ReturnType # 
export {}
type ReturnType<T extends (...args: any[]) => any> = T extends (...args: any[]) => infer R ? R : any;
function getUserInfo() {
    return { name: "zhufeng", age: 10 };
}

// 通过 ReturnType 将 getUserInfo 的返回值类型赋给了 UserInfo
type UserInfo = ReturnType<typeof getUserInfo>;

const userA: UserInfo = {
    name: "zhufeng",
    age: 10
};
10.6.3.5 Parameters # 
export {}
type Parameters<T> = T extends (...args: infer R) => any ? R : any;

type T0 = Parameters<() => string>;  // []
type T1 = Parameters<(s: string) => void>;  // [string]
type T2 = Parameters<(<T>(arg: T) => T)>;  // [unknown]
10.6.3.6 InstanceType # 
type Constructor = new (...args: any[]) => any;
type ConstructorParameters<T extends Constructor> = T extends new (...args: infer P) => any ? P : never;
type InstanceType<T extends Constructor> = T extends new (...args: any[]) => infer R ? R : any;

class Person {
    name: string;
    constructor(name: string) {
        this.name = name;
    }
    getName() { console.log(this.name) }
}
//构造函数参数
type constructorParameters = ConstructorParameters<typeof Person>;
let params: constructorParameters = ['zhufeng']
//实例类型
type Instance = InstanceType<typeof Person>;
let instance: Instance = { name: 'zhufeng', getName() { } };
10.6.3.7 infer+分布式 # 
type ElementOf<T> = T extends Array<infer E> ? E : never;

type TTuple = [string, number];

type ToUnion = ElementOf<TTuple>; // string | number

//联合类型（Union Types）表示取值可以为多种类型中的一种
//交叉类型（Intersection Types）表示将多个类型合并为一个类型
//联合类型转交叉类型
//union 转 intersection
//union 转 intersection 的操作多用于 mixin 中
//https://github.com/Microsoft/TypeScript/issues/27907
type T1 = { name: string };
type T2 = { age: number };

type UnionToIntersection<T> = T extends { a: (x: infer U) => void; b: (x: infer U) => void } ? U : never;
type T3 = UnionToIntersection<{ a: (x: T1) => void; b: (x: T2) => void }>; // T1 & T2

10.7 内置工具类型 #

符号 含义
+? 变为可选
-? 变为必选

10.7.1 Partial # 

type Partial<T> = { [P in keyof T]?: T[P] };

interface A {
  a1: string;
  a2: number;
  a3: boolean;
}

type aPartial = Partial<A>;

const a: aPartial = {}; // 不会报错

10.7.2 类型递归 # 

interface Company {
    id: number
    name: string
}

interface Person {
    id: number
    name: string
    company: Company
}
type DeepPartial<T> = {
    [U in keyof T]?: T[U] extends object
    ? DeepPartial<T[U]>
    : T[U]
};

type R2 = DeepPartial<Person>

10.7.3 Required # 

interface Person{
  name:string;
  age:number;
  gender?:'male'|'female';
}
/**
 * type Require<T> = { [P in keyof T]-?: T[P] };
 */
let p:Required<Person> = {
  name:'zhufeng',
  age:10,
  //gender:'male'
}

10.7.4 Readonly # 

interface Person{
  name:string;
  age:number;
  gender?:'male'|'female';
}
//type Readonly<T> = { readonly [P in keyof T]: T[P] };
let p:Readonly<Person> = {
  name:'zhufeng',
  age:10,
  gender:'male'
}
p.age = 11;

10.7.5 Pick # 

interface Animal {
  name: string;
  age: number;
  gender:number
}
/**
 * From T pick a set of properties K
 * type Pick<T, K extends keyof T> = { [P in K]: T[P] };
 */
// 摘取 Animal 中的 name 属性
interface Person {
    name: string;
    age: number;
    married: boolean
}
function pick<T, K extends keyof T>(obj: T, keys: K[]): Pick<T, K> {
    const result: any = {};
    keys.map(key => {
        result[key] = obj[key];
    });
    return result
}
let person: Person = { name: 'zhufeng', age: 10, married: true };
let result: Pick<Person, 'name' | 'age'> = pick<Person, 'name' | 'age'>(person, ['name', 'age']);
console.log(result);

10.7.6 Record # 

/**
 * Construct a type with a set of properties K of type T
 */
type Record<K extends keyof any, T> = {
    [P in K]: T;
};

function mapObject<K extends string | number, T, U>(obj: Record<K, T>, map: (x: T) => U): Record<K, U> {
    let result: any = {};
    for (const key in obj) {
        result[key] = map(obj[key]);
    }
    return result;
}
let names = { 0: 'hello', 1: 'world' };
let lengths = mapObject<string | number, string, number>(names, (s: string) => s.length);
console.log(lengths);//{ '0': 5, '1': 5 }

type Point = 'x' | 'y';
type PointList = Record<Point, { value: number }>
const cars: PointList = {
    x: { value: 10 },
    y: { value: 20 },
}

10.8 自定义高级类型 #

10.8.1 Proxy # 

type Proxy<T> = {
    get(): T;
    set(value: T): void;
}
type Proxify<T> = {
    [P in keyof T]: Proxy<T[P]>
}
function proxify<T>(obj: T): Proxify<T> {
    let result = {} as Proxify<T>;
    for (const key in obj) {
        result[key] = {
            get: () => obj[key],
            set: (value) => obj[key] = value
        }
    }
    return result;
}
let props = {
    name: 'zhufeng',
    age: 10
}
let proxyProps = proxify(props);
console.log(proxyProps);

function unProxify<T>(t: Proxify<T>): T {
    let result = {} as T;
    for (const k in t) {
        result[k] = t[k].get();
    }
    return result;
}

let originProps = unProxify(proxyProps);
console.log(originProps);

10.8.2 SetDifference # 

/**
 * SetDifference (same as Exclude)
 * @desc Set difference of given union types `A` and `B`
 * @example
 *   // Expect: "1"
 *   SetDifference<'1' | '2' | '3', '2' | '3' | '4'>;
 *
 *   // Expect: string | number
 *   SetDifference<string | number | (() => void), Function>;
 */
export type SetDifference<A, B> = A extends B ? never : A;

10.8.3 Omit # 

/**
 * Omit (complements Pick)
 * @desc From `T` remove a set of properties by key `K`
 * @example
 *   type Props = { name: string; age: number; visible: boolean };
 *
 *   // Expect: { name: string; visible: boolean; }
 *   type Props = Omit<Props, 'age'>;
 */
export type Omit<T, K extends keyof any> = Pick<T, SetDifference<keyof T, K>>;

10.8.4 Diff # 

/**
 * Diff
 * @desc From `T` remove properties that exist in `U`
 * @example
 *   type Props = { name: string; age: number; visible: boolean };
 *   type DefaultProps = { age: number };
 *
 *   // Expect: { name: string; visible: boolean; }
 *   type DiffProps = Diff<Props, DefaultProps>;
 */
export type Diff<T extends object, U extends object> = Pick<
  T,
  SetDifference<keyof T, keyof U>
>;

10.8.5 Intersection # 

/**
 * Intersection
 * @desc From `T` pick properties that exist in `U`
 * @example
 *   type Props = { name: string; age: number; visible: boolean };
 *   type DefaultProps = { age: number };
 *
 *   // Expect: { age: number; }
 *   type DuplicateProps = Intersection<Props, DefaultProps>;
 */
export type Intersection<T extends object, U extends object> = Pick<
  T,
  Extract<keyof T, keyof U> & Extract<keyof U, keyof T>
>;

10.8.6 Overwrite # 

/**
 * Overwrite
 * @desc From `U` overwrite properties to `T`
 * @example
 *   type Props = { name: string; age: number; visible: boolean };
 *   type NewProps = { age: string; other: string };
 *
 *   // Expect: { name: string; age: string; visible: boolean; }
 *   type ReplacedProps = Overwrite<Props, NewProps>;
 */
export type Overwrite<
  T extends object,
  U extends object,
  I = Diff<T, U> & Intersection<U, T>
> = Pick<I, keyof I>;

type Props = { name: string; age: number; visible: boolean };
type NewProps = { age: string; other: string };

// Expect: { name: string; age: string; visible: boolean; }
type ReplacedProps = Overwrite<Props, NewProps>;

10.8.7 Merge # 

type O1 = {
  id: number;
  name: string;
};

type O2 = {
  id: number;
  age: number;
};


//Compute的作用是将交叉类型合并
type Compute<A extends any> = A extends Function ? A : { [K in keyof A]: A[K] };

type R1 = Compute<{ x: "x" } & { y: "y" }>;
type Merge<O1 extends object, O2 extends object> = Compute<
  O1 & Omit<O2, keyof O1>
>;

type R2 = Merge<O1, O2>;

10.8.8 Mutable # 

type Mutable<T> = {
  -readonly [P in keyof T]: T[P]
}

10.9 面试题综合实战 # 

interface Action<T> {
    payload?: T;
    type: string;
}

class EffectModule {
    count = 1;
    message = "hello!";

    delay(input: Promise<number>): Promise<Action<string>> {
        let action: Promise<Action<string>> =  input.then(i => ({
            payload: `hello ${i}!`,
            type: 'delay'
        }));
        return action;
    }

    setMessage(action: Action<Date>): Action<number> {
        let action2: Action<number> = {
            payload: action.payload!.getMilliseconds(),
            type: "set-message"
        };
        return action2;
    }
}
//把 EffectModule 中的方法名取出来
type methodsPick<T> = { [K in keyof T]: T[K] extends Function ? K : never }[keyof T];
//定义转换前后的方法
type asyncMethod<T, U> = (input: Promise<T>) => Promise<Action<U>> // 转换前
type asyncMethodConnect<T, U> = (input: T) => Action<U> // 转换后
type syncMethod<T, U> = (action: Action<T>) => Action<U> // 转换前
type syncMethodConnect<T, U> = (action: T) => Action<U> // 转换后
//条件类型+推断类型
type EffectModuleMethodsConnect<T> = T extends asyncMethod<infer U, infer V>
    ? asyncMethodConnect<U, V>
    : T extends syncMethod<infer U, infer V>
    ? syncMethodConnect<U, V>
    : never
type EffectModuleMethods = methodsPick<EffectModule>
//映射类型
type Connect = (module: EffectModule) => {
    [M in EffectModuleMethods]: EffectModuleMethodsConnect<EffectModule[M]>
} 
type Connected = {
    delay(input: number): Action<string>;
    setMessage(action: Date): Action<number>;
};
const connect: Connect = (m: EffectModule): Connected => ({
    delay: (input: number) => ({
        type: 'delay',
        payload: `hello 2`
    }),
    setMessage: (input: Date) => ({
        type: "set-message",
        payload: input.getMilliseconds()
    })
});

export const connected: Connected = connect(new EffectModule());

11. 模块VS命名空间 #

foo.ts

const foo = 123;

bar.ts

const bar = foo; // allowed
11.1.2 文件模块 # 
export const a = 1;
export const b = 2;
export default 'zhufeng';

import name, { a, b } from './1';
console.log(name, a, b);
11.1.3 模块规范 #

11.2 命名空间 #

11.2.1 内部划分 # 
export namespace zoo {
    export class Dog { eat() { console.log('zoo dog'); } }
}
export namespace home {
    export class Dog { eat() { console.log('home dog'); } }
}
let dog_of_zoo = new zoo.Dog();
dog_of_zoo.eat();
let dog_of_home = new home.Dog();
dog_of_home.eat();

import { zoo } from './3';
let dog_of_zoo = new zoo.Dog();
dog_of_zoo.eat();
11.2.2 原理 # 
namespace Numbers {
    export let a = 1;
    export let b = 2;
    export let c = 3;
}

var Numbers;
(function (Numbers) {
    Numbers.a = 1;
    Numbers.b = 2;
    Numbers.c = 3;
})(Numbers || (Numbers = {}));

11.3 文件，模块与命名空间 #

11.3.1 文件和模块 #

src\table2.ts

export module Box{
    export class Book1{}
}

src\table3.ts

export module Box{
    export class Book1{}
}
11.3.2 空间 #

src\table1.ts

namespace  Box{
    export class Book1{}
}

src\table2.ts

namespace  Box{
    export class Book1{}
}

src\table3.ts

namespace  Box{
    export class Book1{}
}
11.3.3 文件 #

src\table1.ts

export class Book1 { }

src\table2.ts

export class Book1 { }

src\table3.ts

export class Book1 { }

12.类型声明 # 

declare var 声明全局变量
declare function 声明全局方法
declare class 声明全局类
declare enum 声明全局枚举类型
declare namespace 声明(含有子属性的)全局对象
interface 和 type 声明全局类型

12.1 普通类型声明 # 

declare let name: string;  //变量
declare let age: number;  //变量
declare function getName(): string;  //方法
declare class Animal { name: string }  //类
console.log(name, age);
getName();
new Animal();
export default {};

声明jQuery对象

declare const $: (selector: string) => { //变量
    click(): void;
    width(length: number): void;
};
$('#root').click();
console.log($('#root').width);

12.2 外部枚举 # 

declare enum Seasons {
    Spring,
    Summer,
    Autumn,
    Winter
}

let seasons = [
    Seasons.Spring,
    Seasons.Summer,
    Seasons.Autumn,
    Seasons.Winter
];

declare 定义的类型只会用于编译时的检查，编译结果中会被删除。上例的编译结果如下

var seasons = [
    Seasons.Spring,
    Seasons.Summer,
    Seasons.Autumn,
    Seasons.Winter
];

也可以同时使用declare 和 const

declare const enum Seasons {
    Spring,
    Summer,
    Autumn,
    Winter
}

let seasons = [
    Seasons.Spring,
    Seasons.Summer,
    Seasons.Autumn,
    Seasons.Winter
];

编译结果

var seasons = [
    0 /* Spring */,
    1 /* Summer */,
    2 /* Autumn */,
    3 /* Winter */
];

12.3 namespace # 

declare namespace ${
    function ajax(url:string,settings:any):void;
    let name:string;
    namespace fn {
        function extend(object:any):void;
    }
}
$.ajax('/api/users',{});
$.fn.extend({
    log:function(message:any){
        console.log(message);
    }
});
export {};

12.4 类型声明文件 #

12.4.1 jquery.d.ts #

typings\jquery.d.ts

declare const $:(selector:string)=>{
    click():void;
    width(length:number):void;
}

12.4.2 tsconfig.json #

tsconfig.json

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "ES2015",  
    "outDir":"lib"
  },
  "include": [
    "src/**/*",
    "typings/**/*"
  ]
}

12.4.3 test.js #

src\test.ts

$('#button').click();
$('#button').width(100);
export {};

12.5 第三方声明文件 #

12.5.1 使用jquery # 

cnpm i jquery -S

//对于common.js风格的模块必须使用 import * as 
import * as jQuery from 'jquery';
jQuery.ajax('/user/1');

12.5.2 安装声明文件 # 

cnpm i @types/jquery -S

12.5.3 自己编写声明文件 #

12.5.3.1 index.d.ts #

types\jquery\index.d.ts

declare function jQuery(selector:string):HTMLElement;
declare namespace jQuery{
  function ajax(url:string):void
}
export default jQuery;
12.5.3.2 tsconfig.json # 
{
  "compilerOptions": {
    "baseUrl": "./",// 使用 paths 属性的话必须要指定 baseUrl 的值
    "paths": {
      "*":["types/*"]
    }
}

import $ from "jquery";
$.ajax('get');

12.5.4 npm声明文件可能的位置 #

12.5.5 查找声明文件 # 

{
    "name": "myLib",
    "version": "1.0.0",
    "main": "lib/index.js",
    "types": "myLib.d.ts",
}
`

12.6 扩展全局变量的类型 #

12.6.1 扩展局部变量类型 # 

declare var String: StringConstructor;
interface StringConstructor {
    new(value?: any): String;
    (value?: any): string;
    readonly prototype: String;
}
interface String {
    toString(): string;
}

//扩展类的原型
interface String {
    double():string;
}

String.prototype.double = function(){
    return this+'+'+this;
}
console.log('hello'.double());

//扩展类的实例
interface Window{
    myname:string
}
console.log(window.myname);
//export {} 没有导出就是全局扩展

12.6.2 模块内全局扩展 #

types\global\index.d.ts

declare global{
    interface String {
        double():string;
    }
    interface Window{
        myname:string
    }
}

export  {}

12.7 合并声明 #

关键字 作为类型使用 作为值使用
class yes yes
enum yes yes
interface yes no
type yes no
function no yes
var,let,const no yes 
class Person{
    name:string=''
}
let p1:Person;//作为类型使用
let p2 = new Person();//作为值使用

interface Animal{
    name:string
}
let a1:Animal;
let a2 = Animal;//接口类型不能用作值

12.7.1 合并类型声明 #

use.js

interface Animal{
    name:string
}
let a1:Animal={name:'zhufeng',age:10};
console.log(a1.name);
console.log(a1.age);
//注意不要加export {} ,这是全局的

types\animal\index.d.ts

interface Animal{
    age:number
}

12.7.2 使用命名空间扩展类 #

12.7.3 使用命名空间扩展函数 # 

function greeting(name: string): string {
    return greeting.words+name;
}

namespace greeting {
    export let words = "Hello,";
}

console.log(greeting('zhufeng'))

12.7.4 使用命名空间扩展枚举类型 # 

enum Color {
    red = 1,
    yellow = 2,
    blue = 3
}

namespace Color {
    export const green=4;
    export const purple=5;
}
console.log(Color.green)

12.7.5 扩展Store # 

import { createStore, Store } from 'redux';
type StoreExt = Store & {
    ext: string
}
let store: StoreExt = createStore(state => state);
store.ext = 'hello';

12.8 生成声明文件 # 

{
  "compilerOptions": {
     "declaration": true, /* Generates corresponding '.d.ts' file.*/
  }
}

12.9 类型声明实战 # 

npm link
npm link zf-events

12.9.1 index.js # 

import { EventEmitter } from "zf-events";
console.log(EventEmitter.defaultMaxListeners);
var e = new EventEmitter();
e.on('message', function (text:string) {
    console.log(text)
})
e.emit('message', 'hello');

12.9.2 index.d.ts # 

export type Listener = (...args: any[]) => void;
export type Type = string | symbol

export class EventEmitter {
   static defaultMaxListeners: number;
   emit(type: Type, ...args: any[]): boolean;
   addListener(type: Type, listener: Listener): this;
   on(type: Type, listener: Listener): this;
   once(type: Type, listener: Listener): this;
}
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