TypeScript-泛型工具

1.可选泛型

将泛型中的所有属性变为可选.

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type Partial<T> = {
	[P in keyof T]?: T[P]
};

举例:

type Person = {
  name: string;
  age: number;
  gender: string;
  height: number;
  weight: number;
};

再使用Partial包裹

type PartOfPerson = Partial<Person>;

const ben: PartOfPerson = {
  name: 'Ben',
  age: 18,
};

2.将K类型的所有属性转换为T类型

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type Record<K extends keyof any, T> = {
    [P in K]: T;
};

这里的K实际作为键值使用,所以仅可用number|string|symbol类型

举例:

const obj: Record<string, string | number> = {
  name: 'zhangsan',
  age: 18,
  weight: 80,
  gender: '男',
};

interface CatInfo {
  age: number;
  breed: string;
}
 
type CatName = "miffy" | "boris" | "mordred";
 
const cats: Record<CatName, CatInfo> = {
  miffy: { age: 10, breed: "Persian" },
  boris: { age: 5, breed: "Maine Coon" },
  mordred: { age: 16, breed: "British Shorthair" },
};

3.从T类型中提取K的键值列出来组成新的类型

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type Pick<T, K extends keyof T> = {
    [P in K]: T[P];
};

举例:定义一个人的类型

type Person = {
  name: string;
  age: number;
  gender: string;
  height: number;
  weight: number;
};

重新定义一个只有名字和年龄的类型

type NewPerson = Pick<Person, 'name' | 'age'>;

const Mike: NewPerson = {
  name: 'mike',
  age: 20,
};

4.去除T类型和U类型中的交集,取剩余部分

type Exclude<T, U> = T extends U ? never : T;

举例:

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type T1 = Exclude<"a" | "b" | "c", "a" | "b">; // "c"
type T2 = Exclude<string | number | (() => void), Function | string>; // "number"

5.去除T类型中包含的K键值对

type Omit = Pick<T, Exclude<keyof T, K>>

举例:

type Person = {
  name: string;
  age: number;
  gender: string;
  height: number;
  weight: number;
};

去除Person类型中的height和weight属性

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type NewPerson = Omit<Person, 'height' | 'age'>;

const Mike: NewPerson = { name: 'Mike', age: 18, gender: '男' };

6.将类型T中的所有属性变为必选项

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type Required<T> = {
  [P in keyof T]-?: T[P]
}

举例:

type Person = {
  name: string;
  age: number;
  gender: string;
  height?: number;
  weight?: number;
};

将Person中的height和weight属性变为必选项目

type AllPerson = Required<Person>;

const Mike: AllPerson = {
  name: 'Mike',
  age: 18,
  gender: '男',
  height: 180,
  weight: 80,
};

7.获取T类型对应的返回值类型

1	type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;

#### 8.总结