Type

基本类型

es-type.ts

// ES中原有的类型
const nu: null = null;
const un: undefined = undefined;
const bool: boolean = false;
const str: string = "";
const num: number = 0;
const bigNum: bigint = 0n;
const syb: symbol = Symbol("这是一个symbol");

ts-type.ts

// 以下类型 TS 特有
const a: any = "whatever"; //关闭类型检查
const b = a as unknown as string; //类型未知
type funVoid = () => void; //没有返回值
type funNever = () => never; //函数可能会报错

TIP

• unknown 不能直接赋值给其它开启了类型检查变量，与any相比不会关闭其它变量的类型检查

let a: unknown = 123;
let b: number;
b = a; //报错
b = a as number; //不报错
b = <number>a;

引用类型

数组

• array

let arr: string[] = [];
let arr02: array<string> = [];

元组

• tuple, 长度固定的数组

const tuple: [string, string] = ["", ""];

枚举 不推荐

• enum

enum Gender {
  male,
  female,
}
let i: Gender = 99999;
const enum Sex {
  man = 0,
  women = 1,
}
let j = Sex.women;

TIP

枚举的本质是 number 类型

类型字面量

let a: "true" | "false" = "false";
let c: { name: string; age?: number } = { name: "" };
let obj: { name: string; [key: string]: unknown } = { name: "" };
let fun: (b: number, a: number) => number;

联合类型

// 与
let i: { name: string } & { age: number };
// 或
let b: number | string;

类型别名

type numOrStr = number | string;
let i: numOrStr;