Typescrit从入门到放弃系列(二)-基础类型

TS中冒号后面的都为类型标识

一.布尔、数字、字符串类型

let bool:boolean = true;
let num:number = 10;
let str:string = 'hello zf';

二.元组类型

限制长度个数、类型一一对应

let tuple:[string,number,boolean] = ['james',18,true];
// 像元组中增加数据，只能增加元组中存放的类型
tuple.push('深圳');

三.数组

声明数组中元素数据类型

let arr1:number[] = [1,2,3];
let arr2:string[] = ['1','2','3'];
let arr3:(number|string)[] = [1,'2',3];
let arr4:Array<number | string> = [1,'2',3]; // 泛型方式来声明

四.枚举类型

enum USER_ROLE {
    USER, // 默认从0开始
    ADMIN,
    MANAGER
}
// {0: "USER", 1: "ADMIN", 2: "MANAGER", USER: 0, ADMIN: 1, MANAGER: 2}

可以枚举，也可以反举

// 编译后的结果
(function (USER_ROLE) {
    USER_ROLE[USER_ROLE["USER"] = 0] = "USER";
    USER_ROLE[USER_ROLE["ADMIN"] = 1] = "ADMIN";
    USER_ROLE[USER_ROLE["MANAGER"] = 2] = "MANAGER";
})(USER_ROLE || (USER_ROLE = {}));

异构枚举

enum USER_ROLE {
    USER = 'user',
    ADMIN = 1,
    MANAGER,
}

常量枚举

const enum USER_ROLE {
    USER,
    ADMIN,
    MANAGER,
}
console.log(USER_ROLE.USER)// console.log(0 /* USER */);

五.any类型

不进行类型检测

let arr:any = ['james',true,{name:'golderbrother'}]

六.null 和 undefined

任何类型的子类型,如果strictNullChecks的值为true，则不能把null 和 undefined付给其他类型

let name:number | boolean;
name = null;

七.void类型

只能接受null，undefined。一般用于函数的返回值

let a:void;
a = undefined;

八.never类型

任何类型的子类型,never代表不会出现的值。不能把其他类型赋值给never

function error(message: string): never {
    throw new Error("err");
}
function loop(): never {
    while (true) { }
}
function fn(x:number | string){
    if(typeof x == 'number'){

    }else if(typeof x === 'string'){

    }else{
        console.log(x); // never
    }
}

function error(message: string): never {
    throw new Error("err");
}
function loop(): never {
    while (true) { }
}
function fn(x:number | string){
    if(typeof x == 'number'){

    }else if(typeof x === 'string'){

    }else{
        console.log(x); // never
    }
}

function error(message: string): never {
    throw new Error("err");
}
function loop(): never {
    while (true) { }
}
function fn(x:number | string){
    if(typeof x == 'number'){

    }else if(typeof x === 'string'){

    }else{
        console.log(x); // never
    }
}

九.Symbol类型

Symbol表示独一无二

const s1 = Symbol('key');
const s2 = Symbol('key');
console.log(s1 == s2); // false

十.BigInt类型

const num1 = Number.MAX_SAFE_INTEGER + 1;
const num2 = Number.MAX_SAFE_INTEGER + 2;
console.log(num1 == num2)// true


let max: bigint = BigInt(Number.MAX_SAFE_INTEGER)
console.log(max + BigInt(1) === max + BigInt(2))

十一.object对象类型

object表示非原始类型

let create = (obj:object):void=>{}
create({});
create([]);
create(function(){})