TS/part1/02.ts

// 类型 
// number string boolean 字面量 any void
// unknown never object array tuple enum

// 隐式类型any
let d;
d = 10;
d = "333";
d = true;

// 隐式any类型缺点，any值可以赋给其他不同类型
let s: string;
s = d; 

let e: unknown;
// s = e; unknown不能赋值其他

// unknown赋给其他值方法
// 方法1.先判断
if(typeof e === "string"){
    s = e;
}
// 方法2.类型断言
s = e as string;
// 另外写法
s = <string>e;

function fn(): void{}

function fn1(): never{
    throw new Error('ddd');
}

// 指定属性,有问号的可以不对应
let obj1: {name: string, age?: number};
obj1 = {name: 'sss'}

// 任意属性
let obj2: {name: string, [propName: string]: any};
obj2 = {name: 'sss', xxx:'sssss', xxxx: 23}

let fff: (a: number, b: number)=> number;
fff = function(n1: number ,n2: number):number{
    return n1 + n2
}

// 数组
let arr: string[];
let arr2: Array<number>

// 元组，固定长度数组
let h: [string, string];
h = ['ss','ff']

// 枚举
enum Gender{Male,Female}
let i: {name: string, gender: Gender};
i = {name:'dd', gender: Gender.Female};