TS高级类型内置工具类型-技术圈

TS高级类型内置工具类型

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· 2021-04-08

Partial<T>

将泛型 T 中的所有属性转化为可选属性

/** * Make all properties in T optional */type Partial<T> = {    [P in keyof T]?: T[P];};
interface IUser {  name: string;  age: number;}
type t = Partial<IUser>;/* type t = {    name?: string;    age?: number} */

Required<T>

将泛型 T 中的所有属性转化为必选属性

/** * Make all properties in T required */type Required<T> = {    [P in keyof T]-?: T[P];};
interface IUser {  name?: string;  age?: number;}
type t = Required<IUser>;/* type t = {    name: string;    age: number} */

Readonly<T>

将泛型 T 中的所有属性转化为只读属性

/** * Make all properties in T readonly */type Readonly<T> = {    readonly [P in keyof T]: T[P];};
interface IUser {  name: string;  age: number;}
type t = Readonly<IUser>;/* type t = {    readonly name: string;    readonly age: number} */

Pick<T, K extends keyof T>

从泛型 T 中检出指定的属性并组成一个新的对象类型

/** * From T, pick a set of properties whose keys are in the union K */type Pick<T, K extends keyof T> = {    [P in K]: T[P];};
interface IUser {  name: string;  age: number;  address: string;}
type t = Pick<IUser, 'name' | 'age'>;/* type t = {    name: string;    age: number} */

Record<K extends keyof any, T>

Record 允许从 Union 类型中创建新类型，Union 类型中的值用作新类型的属性。

经常用于接口 response 类型声明

/** * Construct a type with a set of properties K of type T */type Record<K extends keyof any, T> = {    [P in K]: T;};
type Car = 'Audi' | 'BMW' | 'MercedesBenz'type CarList = Record<Car, {age: number}>
const cars: CarList = {    Audi: { age: 119 },    BMW: { age: 113 },    MercedesBenz: { age: 133 },}

Exclude<T, U>

从泛型 T 中排除可以赋值给泛型 U 的类型

/** * Exclude from T those types that are assignable to U */type Exclude<T, U> = T extends U ? never : T;
type a = 1 | 2 | 3;
type t = Exclude<a, 1 | 2>;/* type t = 3 */

Extract<T, U>

从泛型 T 中提取可以赋值给泛型 U 的类型

/** * Extract from T those types that are assignable to U */type Extract<T, U> = T extends U ? T : never;
type a = 1 | 2 | 3;
type t = Extract<a, 1 | 2>;/* type t = 1 | 2 */

Omit<T, K extends keyof any>

从泛型 T 中提取出不在泛型 K 中的属性类型，并组成一个新的对象类型

/** * Construct a type with the properties of T except for those in type K. */type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
interface IUser {  name: string;  age: number;  address: string;}
type t = Omit<IUser, 'name' | 'age'>;/* type t = {    address: string;} */

NonNullable<T>

从泛型 T 中排除掉 null 和 undefined

/** * Exclude null and undefined from T */type NonNullable<T> = T extends null | undefined ? never : T;
type t = NonNullable<'name' | undefined | null>;/* type t = 'name' */

Parameters<T extends (...args: any) => any>

以元组的方式获得函数的入参类型

/** * Obtain the parameters of a function type in a tuple */type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : never;
type t = Parameters<(name: string) => any>; // type t = [string]type t2 = Parameters<((name: string) => any)  | ((age: number) => any)>; // type t2 = [string] | [number]

ConstructorParameters<T extends new (...args: any) => any>

以元组的方式获得构造函数的入参类型

/** * Obtain the parameters of a constructor function type in a tuple */type ConstructorParameters<T extends new (...args: any) => any> = T extends new (...args: infer P) => any ? P : never;
type t = ConstructorParameters<(new (name: string) => any)  | (new (age: number) => any)>;// type t = [string] | [number]

ReturnType<T extends (...args: any) => any>

获得函数返回值的类型

/** * Obtain the return type of a function type */type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;
type t = ReturnType<(name: string) => string | number>// type t = string | number

InstanceType<T extends new (...args: any) => any>

获得构造函数返回值的类型

/** * Obtain the return type of a constructor function type */type InstanceType<T extends new (...args: any) => any> = T extends new (...args: any) => infer R ? R : any;
type t = InstanceType<new (name: string) => {name: string, age: number}>/* type h = {    name: string;    age: number;}*/

总结：

1、重点理解这些内置的工具类型的定义。

2、能够以此为参考写一些工具类型并运用到项目中去。