TypeScript Advanced Types All In One

lib.es5.d.ts

https://github.com/microsoft/TypeScript/blob/main/lib/lib.es5.d.ts#L1499

// ...

/**
 * Make all properties in T optional
 */
type Partial = {
    [P in keyof T]?: T[P];
};

/**
 * Make all properties in T required
 */
type Required = {
    [P in keyof T]-?: T[P];
};

/**
 * Make all properties in T readonly
 */
type Readonly = {
    readonly [P in keyof T]: T[P];
};

/**
 * From T, pick a set of properties whose keys are in the union K
 */
type Pick = {
    [P in K]: T[P];
};

/**
 * Construct a type with a set of properties K of type T
 */
type Record = {
    [P in K]: T;
};

// ...

Mapped Types

type Record = {
  [P in K]: T;
};

https://www.typescriptlang.org/docs/handbook/advanced-types.html#mapped-types
https://www.typescriptlang.org/docs/handbook/2/mapped-types.html

type Partial = {
  [P in keyof T]?: T[P];
};
 
type Readonly = {
  readonly [P in keyof T]: T[P];
};

demo

type PersonPartial = Partial;
// 等价于 
type PersonPartial = {
    name?: string | undefined;
    age?: number | undefined;
}

type ReadonlyPerson = Readonly;
// 等价于     
type ReadonlyPerson = {
    readonly name: string;
    readonly age: number;
}

Utility Types

const test: Beacon ???

Record

https://www.typescriptlang.org/docs/handbook/utility-types.html#recordkeys-type

refs

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