实体类型

在ts中内置了许多实体类，简化声明类型

Partial

将对象中的属性都声明为可选的

Required

将对象中的属性都声明为必须的

Record

声明指定类型key和指定类型的value构成对象

const obj: Record<string, number> = {xiaohua: 23, xiaoming: 26}
// 等价于
const obj2: { [key: string]: number } = {xiaohua: 23, xiaoming: 26}

Omit

忽略对象的属性，第二个类型变量为union type

interface Person {
    name: string;
    age: number;
    location?: string;
}

const a: Omit<Person, 'age'> = {
    name: '',
    location: '',
}

Pick

只取对象中指定属性，第二个类型变量与Omit相同为union type

Exclude

去除union type的指定类型

type Primitive = string | number | boolean
const value: Exclude<Primitive, string> = true

ReturnType

提取函数类型的返回值的类型

type introduce = () => string
const value: ReturnType<introduce> = '123'

Parameters

提取参数列表的类型，并构成一个array

type introduce = (name: string, age: number) => void

const nickName: Parameters<introduce>[0] = '123'

Readonly

基于现有类型创建一个属性只读的类型，一旦赋值便无法更改

interface Person {
    name: string;
    age: number;
}

const person: Readonly<Person> = {
    name: "Dylan",
    age: 35,
};
// TS2540: Cannot assign to 'name' because it is a read-only property.
// person.name = 'Israel';