TypeScript 的高级类型

typescript

字数统计: 816阅读时长: 4 min

 2022/09/27 

Record

给若干个参数创建属性

type Coord = Record<'x' | 'y', number>;

// 等同于
type Coord = {
	x: number;
	y: number;
}

Pick

选择若干个参数

type Coord = {
	x: number;
	y: number;
}

type CoordX = Pick<Coord, x>

type CoordX = {
 	x: number;
}

Readonly

只读

type Coord = {
	x: number;
	y: number;
}

type CoordX = Readonly<Coord>

type CoordX = {
 	readonly x: number;
  readonly y: number;
}

Partial

参数可选。

type Coord = {
	x: number;
	y: number;
}

type CoordX = Partial<Coord>

type CoordX = {
 	x?: number;
  y?: number;
}

Required

与 Partial 相反

type Coord = {
	x?: number;
	y?: number;
}

type CoordX = Required<Coord>

type CoordX = {
 	x: number;
  y: number;
}

Exclude

1	type T0 = Exclude<'a' \| 'b' \| 'c', 'b'> // 'a' \| 'c'

Extract

1	type T0 = Exclude<'a' \| 'b' \| 'c', 'b' \| 'd'> // 'b'

Omit

type Omit<T**, **K** **extends** **keyof** **any> = Pick<**T**, **Exclude**<keyof **T**, **K**>>;

interface I1 {
	a: number;
	b: string;
	c: boolean;
}

type AC = Omit<I1, 'b'>;     // { a:number; c:boolean } 
type C = Omit<I1, 'a' |'b'>  // { c: boolean }

NonNullable

1	type T1 = NonNullable<string \| null \| undefined>; // string

Parameters

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type F1 = (a: string, b: number) => void;

type F1ParamTypes = Parameters(F1);  // [string, number]

ConstructorParameters

interface IEntity {
    count?: () => number
}

interface IEntityConstructor {
    new (a: boolean, b: string): IEntity;
}

class Entity implements IEntity {
    constructor(a: boolean, b: string) { }
}

type EntityConstructorParamType = ConstructorParameters<IEntityConstructor>; // [boolean, string]

function createEntity(ctor: IEntityConstructor, ...arg: EntityConstructorParamType): IEntity {
    return new ctor(...arg);
}

const entity = createEntity(Entity, true, 'a');

ReturnType

返回函数返回的对象的类型

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type F1 = () => Date;

type F1ReturnType = ReturnType<F1>; // Date

InstanceType

返回 new 类型的 interface 返回的对象。

1	type EntityType = InstanceType<IEntityConstructor>; // IEntity

ThisParameterType

对象中 this 的类型。

interface Foo {
    x: number
};

function fn(this: Foo) {}

type Test = ThisParameterType<typeof fn>; // Foo

OmitThisParameter

移除 this 的数据类型，函数中无法使用 this。

interface Foo {
    x: number
};

type Fn = (this: Foo) => void

type NonReturnFn = OmitThisParameter<Fn>; // () => void

表格

方法	实现
Partial<T>	type Partial<T> = { [P in keyof T]?: T[P]; };
Readonly<T>	type Readonly<T> = { readonly [P in keyof T]: T[P]; };
Pick<T, K extends keyof T>	type Pick<T, K extends keyof T> = { [P in K]: T[P]; };
Record<K extends keyof any, T>	type Record<K extends keyof any, T> = { [P in K]: T; };
Required< T >	type Required<T> = { [P in keyof T]-?: T[P]; };
Exclude<T, U>	type Exclude<T, U> = T extends U ? never : T;
Extract<T, U>	type Extract<T, U> = T extends U ? T : never;
Omit<T, K extends keyof any>	type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;
NonNullable< T >	type NonNullable<T> = T extends null
Parameters<T extends (…args: any) => any>	type Parameters<T extends (…args: any) => any> = T extends (…args: infer P) => any ? P : never;
ConstructorParameters<T extends new (…args: any) => any>	type ConstructorParameters<T extends new (…args: any) => any> = T extends new (…args: infer P) => any ? P : never;
ReturnType<T extends (…args: any) => any>	type ReturnType<T extends (…args: any) => any> = T extends (…args: any) => infer R ? R : any;
InstanceType<T extends new (…args: any) => any>	type InstanceType<T extends new (…args: any) => any> = T extends new (…args: any) => infer R ? R : any;
ThisParameterType< T >	type ThisParameterType<T> = T extends (this: infer U, …args: any[]) => any ? U : unknown;
OmitThisParameter< T >	type OmitThisParameter<T> = unknown extends ThisParameterType<T> ? T : T extends (…args: infer A) => infer R ? (…args: A) => R : T;