Typescript模块的导入导出与继承方式

export let x = 8888;
export let print = function (x){console.log(x);};

export let x = 8888;
export let print = function (x){console.log(x);};

export * as B from "./ModB";
export {H,Hello}  from "./ModB.js";
export {Hello as exp}  from "./ModB.js";

//导出变量
export let HeadName = 'Nance';
export let MidName = 'Jone';
export let BothDate = '2020-12-20';
 
let [X,Y,Z]=[0,0,0];
export {X,Y,Z};
 
//导出函数
export function Add(a,b){return a+b;}
 
function Multiply(x,y){return x * y;}
export {Multiply};
 
function a1(a,b){return a+b;}
function b1(a,b){return a-b;};
export {a1,b1};//导出多个函数
 
//函数别名形式导出
export {a1 as ADD_FUNC ,b1 as DEL_FUNC};
 
//默认导出,一个模块只能有一个默认导出,不管是类,方法或者是变量
//export default class a{};//默认导出类a后就不能再默认导出函数,或者默认导出变量
//export default function b(){};
let qq=0;
export default qq; //默认导出不能使用 as 别名导出

import {HeadName,MidName,BothDate,X,Y,Z,ADD_FUNC,DEL_FUNC,Add} from "./ExportEx";
export {ADD_FUNC,DEL_FUNC,Add as myAdd} from "./ExportEx";//从导入模块直接导出方法
console.log(HeadName,MidName,BothDate);
console.log(X,Y,Z);
console.log(ADD_FUNC(1,2),DEL_FUNC(3,4));
console.log(Add(5,6));

// (newName: string) => void: 这就是类型, 对一个函数进行约束.
// 利用接口对函数进行约束, 描述一个函数的结构, 有什么参数, 什么返回值.
interface FunctionType {
  (newName: string, newAge: number, test?: string): void;
}

let setMyName: FunctionType = function (
  name: string,
  age: number,
  a?: string
): void {
  console.log(name + age);
};
setMyName("新名称", 100);

// 利用接口定义类的结构, 对类中的属性和方法进行约束.
interface AnimalType {
  aname: string;
  eat(n: string): void;
}

// implements 表示一个类要实现某个接口, 必须按照接口的要求, 实现这个类的内部结构.
class Animal implements AnimalType {
  aname: string;
  constructor() {
    this.aname = "鸭子";
  }
  eat(a: string): string {
    return "123";
  }
}
let ani = new Animal();
console.log(ani.eat("1"));

// 制作泛型接口, 用T来表示广泛的类型, 就看使用的时候, 传递的是什么类型.
interface PType<T> {
  p: T;
  p1: T;
}

type PTypeOne<T> = {
  p: T;
  p1: T;
};

let pp1: PTypeOne<string> = {
  p: "123",
  p1: "222",
};

let pp2: PType<number> = {
  p: 12,
  p1: 22,
};

let pp3: PType<number[]> = {
  p: [1, 2, 3],
  p1: [4, 5, 6],
};

// 制作泛型函数
function getValue<T>(a: T, b: T): T {
  return (a as any) + (b as any);
}
console.log(getValue<string>("10", "20"));
console.log(getValue<number>(10, 20));

function getResult<T, Y>(a: T, b: Y): any {
  return (a as any) + (b as any);
}
console.log(getResult<string, number>("10", 20));

// 对于联合类型比较长的情况，可以通过type关键字，给这个联合类型起个别名(相当于自定义了一种新类型)。重用的时候写起来方便。
type baseTypeArr = (number | string | boolean)[];

// number | string | boolean | number[]: 联合类型，表示当前这个变量，允许接收number/string/boolean/number[]这几个类型中的一个即可。
type baseType = number | string | boolean | number[];

// 对于初始值可能为null/undefined的类型，也使用联合类型约束
declare type dataType = string | undefined;
declare type arrType = number[] | null;

// declare 声明类型 namespace 命名空间 ，每个命名空间内都是独立作用域，其实就是将不同的类型放到各自的模块内，统一管理。
namespace HomeType {
  type homeList = number | string;
}

declare namespace CateType {
  type cateList = number | string;
}

declare namespace CartType {
  type cartList = number | string;
}

// 自定义类型，叫People类型
// psex?: boolean 表示People类型中的psex属性可有可无
type People = {
  page: number;
  pname: string;
  psex?: boolean | undefined;
};

type CommonObject = {
  // [propName: string | number]: string | number | boolean; // [propName: string] 接收任意key，且是字符串。
  [propName: string | number]: any; // any：让一个变量可以是任意类型的值，被any标识的数据，ts会放弃对它的检查，而是直接通过编译，ts失效了。一定是在不确定类型/类型不统一是才使用any。
};

declare interface MyPeople {
  pname: string;
  page: number;
  psex?: boolean;
}

   // 普通枚举
   enum Witcher {
     Ciri = 'Queen',
     Geralt = 'Geralt of Rivia'
   }
   function getGeraltMessage(arg: {[key: string]: string}): string {
     return arg.Geralt
   }
   getGeraltMessage(Witcher) // Geralt of Rivia
 
   // const枚举
   const enum Witcher {
     Ciri = 'Queen',
     Geralt = 'Geralt of Rivia'
   }
   const witchers: Witcher[] = [Witcher.Ciri, Witcher.Geralt]
   // 编译后
   // const witchers = ['Queen', 'Geralt of Rivia'

  type Name = { name: string }
  type Age = { age: number }
  type UNIOn = Name | Age
  
  type UnionKey<P> = P extends infer P ? keyof P : never
  
  type T = UnionKey<Union>

type A = {
    a: string;
    b: number;
}

type B = {
    [K in keyof A]?: A[K]
}

type C = {
    [K in keyof B]-?: B[K]
}

type D = {
    readonly [K in keyof A]: A[K]
}

type E = {
    -readonly [K in keyof A]: A[K]
}

interface Named { name: string }
class Person {
  name: string
}
let p: Named
// ok
p = new Person()

// type '"hello"'
let x = "hello" as const
// type 'readonly [10, 20]'
let y = [10, 20] as const
// type '{ readonly text: "hello" }'
let z = { text: "hello" } as const

  declare global {
    interface Window {
      myCustomFn: () => void;
    }
  }

let aaa: [string, number] = ['aaa', 5];
// 添加时不会报错
aaa.push(6);
// 打印整个元祖不会报错
console.log(aaa); // ['aaa',5,6];
// 打印添加的元素时会报错
console.log(aaa[2]); // error

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);