TS高級類型內(nèi)置工具類型
Partial<T>
將泛型 T 中的所有屬性轉(zhuǎn)化為可選屬性
/*** 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>
將泛型 T 中的所有屬性轉(zhuǎn)化為必選屬性
/*** 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>
將泛型 T 中的所有屬性轉(zhuǎn)化為只讀屬性
/*** 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>
從泛型 T 中檢出指定的屬性并組成一個新的對象類型
/*** 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 允許從 Union 類型中創(chuàng)建新類型，Union 類型中的值用作新類型的屬性。
經(jīng)常用于接口 response 類型聲明
/*** 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>
從泛型 T 中排除可以賦值給泛型 U 的類型
/*** 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>
從泛型 T 中提取可以賦值給泛型 U 的類型
/*** 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>
從泛型 T 中提取出不在泛型 K 中的屬性類型，并組成一個新的對象類型
/*** 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>
從泛型 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>
以元組的方式獲得函數(shù)的入?yún)㈩愋?/p>/** * 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>
以元組的方式獲得構(gòu)造函數(shù)的入?yún)㈩愋?/p>/** * 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>
獲得函數(shù)返回值的類型
/*** 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>
獲得構(gòu)造函數(shù)返回值的類型
/*** 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;}*/
總結(jié)：
1、重點理解這些內(nèi)置的工具類型的定義。
2、能夠以此為參考寫一些工具類型并運用到項目中去。