Record

Record 的定义

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

Record 的使用

type Score = Record<string, number>;
const score: Score = { math: 90, english: 90 };
console.log(score);

type Role = 'admin' | 'user' | 'guest';
type Permission = Record<Role, boolean>;
const perms: Permission = { admin: true, user: false, guest: false };

console.log(perms);

// 1. keyof
type User = { name: string; age: number };
type UserFlags = Record<keyof User, boolean>;

const u: UserFlags = {
  name: true,
  age: true
};

console.log(u);

// 2. 嵌套 record
type NestedConfig = Record<string, Record<string, number>>;
const config: NestedConfig = {
  server: {
    port: 8080,
    timeout: 3000
  }
};

// 3. 联合类型
type Status = Record<string, 'active' | 'inactive' | 'pending'>;
const s: Status = {
  a: 'active',
  b: 'inactive',
  c: 'pending'
};

// 4. 结合泛型构建动态映射
function toMap<T>(arr: T[], key: keyof T): Record<string, T> {
  return arr.reduce(
    (acc: Record<string, T>, item: T) => {
      acc[String(item[key])] = item;
      return acc;
    },
    {} as Record<string, T>
  );
}