TypeScript中括号用法小结

let a: {
    b: number;
    c?: string;
    // 注意当key是string的时候，那么确定属性和可选属性的类型必须是它的属性的子集。
    // eg：[key: string]: string | number;
    [key: number]: boolean;
}
a = {
    b: 1;
    c: 'hey';
    20: false;
}

interface Person{
    name: string;
    age: number;
}
// keyof Person => "name" | "age"
type student = Person[keyof Person];
let stu1: student = 'tom';

interface Person{
    name: string;
    age: number;
}
// in keyof Person => 遍历 name，string
// per2 = {
//    name: string;
//    age: number;
//}
type per2 = {
  [P in keyof Person]: Person[P];
};
let a: per2 = {
  name: "tom",
  age: 12
};

type per2 = {
  [P in keyof Person]: Person[P];
}[];
// per2 => Person[];
let c: per2 = [
  {
    name: "tom",
    age: 12,
  },
];

type per2 = {
  [P in keyof Person]: Person[P];
}[keyof Person];
// per2 => "string" | "name"
let c: per2 = "tom";