TypeScript中索引签名的实现示例

interface SomeObject {
  [key: string]: string;
}

interface Dictionary {
  [key: string]: number;
}

const dict: Dictionary = {
  age: 30,
  height: 175
};

console.log(dict["age"]); // 输出: 30
console.log(dict["height"]); // 输出: 175

interface MixedDictionary {
  [key: string]: number;
  [index: number]: number; // 字符串索引与数字索引共享相同的值类型
}

const dict: MixedDictionary = {
  age: 25,
  100: 500,
  height: 175
};

console.log(dict["age"]); // 输出: 25
console.log(dict[100]); // 输出: 500

interface MyObject {
  [key: "a" | "b" | "c"]: number;
}

const obj: MyObject = {
  a: 1,
  b: 2,
  c: 3
};

console.log(obj.a); // 输出: 1

interface ReadOnlyDict {
  readonly [key: string]: number;
}

const readOnlyDict: ReadOnlyDict = {
  age: 30,
  height: 175
};

console.log(readOnlyDict["age"]); // 输出: 30
// readOnlyDict["age"] = 35;  // Error: Cannot assign to 'age' because it is a read-only property.

class MyClass {
  [key: string]: string;

  constructor() {
    this["name"] = "John";
  }
}

const obj = new MyClass();
obj["age"] = "30"; // 可以动态添加新的属性
console.log(obj.name); // 输出: John
console.log(obj.age); // 输出: 30

interface EventDetails {
  [key: string]: "start" | "end"; // 值只能是 "start" 或 "end"
}

const event: EventDetails = {
  event1: "start",
  event2: "end"
};

console.log(event["event1"]); // 输出: start

interface Car {
  make: string;
  model: string;
  [key: string]: string | number; // 支持字符串或数字类型的任意额外属性
}

const car: Car = {
  make: "Toyota",
  model: "Corolla",
  year: 2020, // 额外的属性
  color: "Red"
};

console.log(car);

type DynamicProperties = {
  [key: string]: string;
};

const dynamicObject: DynamicProperties = {
  name: "Alice",
  age: "25",
  occupation: "Engineer"
};

console.log(dynamicObject);

interface DynamicObject {
  [key: string]: string | number;
}

const obj: DynamicObject = {
  name: "Alice",
  age: 30
};

console.log(obj["name"]); // 输出: Alice
console.log(obj["age"]); // 输出: 30

interface Name {
  name: string;
}

interface Address {
  address: string;
}

type Person = Name &
  Address & {
    [key: string]: string; // 任意的额外属性
  };

const person: Person = {
  name: "John",
  address: "123 Main St",
  phone: "123-456-7890"
};

console.log(person);