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';

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);
}
greeting('zfpx');

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);
}

// 由类型推论得到返回值为 never
function fail() {
    return error("Something failed");
}

// 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 类型推论 # 

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

3.12 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

3.13 联合类型 # 

let name4: string | number;
name4 = 3;
name4 = 'zhufeng';
console.log(name4.toUpperCase());

3.14 类型断言 # 

let name5: string | number;
(name5 as number).toFixed(3);
(name5 as string).length;
(name5 as boolean);

3.15 字符串、数字、布尔值字面量 # 

type Lucky = 1 | 'One'|true;
let foo:Lucky = 'One';

3.16 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);
}
hello('zfpx');
hello2('zfpx');

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 === 'number') {
        obj.age=val;
    } else {
        obj.name=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();

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);

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) {
        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 抽象类 # 


abstract class Animal3 {
    name:string;
    abstract speak();
}
class Cat extends Animal3{
    speak(){
        console.log('喵喵喵');
    }
}
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

5.9 抽象类 vs 接口 # 

abstract class Animal5{
  name:string;
  constructor(name:string){
    this.name = name;
  }
  abstract speak();
}
interface Flying{
    fly()
}
class Duck extends Animal5 implements Flying{
    speak(){
        console.log('汪汪汪');
    }
    fly(){
        console.log('我会飞');
    }
}
let duck = new Duck('zhufeng');
duck.speak();
duck.fly();

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 Cat6 extends Animal6{
    speak(word:string):string{
        return 'Cat:'+word;
    }
}
let cat6 = new Cat6();
console.log(cat6.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 Animal7{
    speak(word:string):string{
        return 'Animal: '+word;
    }
}
class Cat7 extends Animal7{
    speak(word:string):string{
        return 'Cat:'+word;
    }
}
class Dog7 extends Animal7{
    speak(word:string):string{
        return 'Dog:'+word;
    }
}
let cat7 = new Cat7();
console.log(cat7.speak('hello'));
let dog7 = new Dog7();
console.log(dog7.speak('hello'));

6. 接口 #

6.1 接口 # 

//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 = {
  name:string;//多属性也会报错
  speak(){}//少属性会报错
}

//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
}
class Person5 implements Speakable,Eatable{
    speak(){
        console.log('Person5说话');
    }
    eat(){}
}
class TangDuck implements Speakable{
    speak(){
        console.log('TangDuck说话');
    }
    eat(){}
}

//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 Person5 implements SpeakChinese{
  speak(){
    console.log('Person5')
  }
  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){
    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){
  }
}
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);

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);

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);

function createArray2<T>(length: number, value: T): Array<T> {
  let result: T[] = [];
  for (let i = 0; i < length; i++) {
    result[i] = value;
  }
  return result;
}
let result2 = createArray2<string>(3,'x');
console.log(result);

7.2 类数组 # 

function sum(...parameters:number[]){
  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.children;
children.length;
let nodeList:NodeList = root.childNodes;
nodeList.length;

7.3 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);

7.5 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)
}
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(1);
logger2('zhufeng');

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 泛型类型别名 # 

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

7.11 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;
  gender:number
}

let a1 = {
  name:'zhufeng',
  age:10,
  gender:0
}

interface Person{
  name:string;
  age:number
}
////- 要判断目标类型`Person`是否能够兼容输入的源类型`Animal`
function getName(p:Person):string{
  return p.name;
}
getName(a1);
//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 x:Person = {
  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;
num = str;

//只要有toString()方法
let num2 : {
  toString():string
}

let str2:string;
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 # 

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


type GetPerson = ()=>{name:string,age:number};
let getPerson:GetPerson;
//参数一样可以
function g1(){
    return {name:'zhufeng',age:10};
}
getPerson = g1;
//多一个属性也可以
function g2(){
    return {name:'zhufeng',age:10,gender:'male'};
}
getPerson = g2;
//少一个属性不行
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 函数参数的双向协变 # 

type LogFunc = (a:number|string)=>void;
let log:LogFunc;
function log1(a:number){
  console.log(a);
}
//在这里定义的参数类型兼容实际的参数类型
log = log1;

function log2(a:number|string|boolean){
  console.log(a);
}
//在这里实际的参数类型兼容定义的参数类型
log = log2;

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
interface Empty<T>{}
let x:Empty<string>;
let y:Empty<number>;
x = y;

//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;

interface NotEmptyString{
    data:string
}

interface NotEmptyNumber{
    data:number
}
let xx3:NotEmptyString;
let yy3:NotEmptyNumber;
xx3 = yy3;

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 #

9.2 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，需要加链判断运算符
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

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);
 }
}

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 # 

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;
}

10. 类型变换 #

10.1 交叉类型 #

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;
}

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 内置工具类型 # 

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

10.6.2 Required # 

/**
 * Make all properties in T required
 */
type Required<T> = { [P in keyof T]-?: T[P] };

interface Person{
  name:string;
  age:number;
  gender?:'male'|'female';
}
let p:Required<Person> = {
  name:'zhufeng',
  age:10,
  //gender:'male'
}

10.6.3 Readonly # 

/**
 * Make all properties in T readonly
 */
type Readonly<T> = { readonly [P in keyof T]: T[P] };

interface Person{
  name:string;
  age:number;
  gender?:'male'|'female';
}
let p:Readonly<Person> = {
  name:'zhufeng',
  age:10,
  gender:'male'
}
p.age = 11;

10.6.4 Pick # 

/**
 * From T pick a set of properties K
 */
type Pick<T, K extends keyof T> = { [P in K]: T[P] };

interface Animal {
  name: string;
  age: number;
}
// 摘取 Animal 中的 name 属性
type AnimalSub = Pick<Animal, "name">; // { name: string; }

10.6.5 映射类型修饰符的控制 #

10.7 条件类型 #

10.7.1 定义条件类型 # 

interface Fish{
  name:string
}
interface Water{
  name:string
}
interface Bird{
  name:string
}
interface Sky{
  name:string
}
//三元运算符
type Condition<T> = T extends Fish?Water:Sky;
let con:Condition<Fish> = {name:'水'};

10.7.2 条件类型的分发 # 

interface Fish{
  name:string
}
interface Water{
  name1:string
}
interface Bird{
  name:string
}
interface Sky{
  name2:string
}
//三元运算符
type Condition<T> = T extends Fish?Water:Sky;
let con1:Condition<Fish|Water> = {name1:'水'};
let con2:Condition<Fish|Water> = {name2:'水'};

10.7.3 内置条件类型 # 

Exclude<T, U> // 从 T 可分配给的类型中排除 U。
Extract<T, U> // 从 T 可分配的类型中提取 U。
NonNullable<T> // 从 T 中排除 null 和 undefined。
ReturnType<T> // 获取函数类型的返回类型。
InstanceType<T> // 获取构造函数类型的实例类型。
10.7.3.1 Exclude # 
type  E = Exclude<string|number,string>;
let e:E = 10;
10.7.3.2 Extract # 
type  E = Extract<string|number,string>;
let e:E = '1';
10.7.3.3 NonNullable # 
type  E = NonNullable<string|number|null|undefined>;
let e:E = null;
10.7.3.4 ReturnType # 
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
};
10.7.3.5 InstanceType # 
class Person{
  name:string;
  constructor(name){
    this.name = name;
  }
  getName(){console.log(this.name)}
}

type  P = InstanceType<typeof Person>;
let p:P = {name:'zhufeng',getName(){}};
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