How to defined dynamic property in typescript

Question

i want create a array-like class

class Demo {
  constructor() {
    [1, 2, 3, 4, 5].forEach((v, i)=> this[i] = v);
  }
}

let demo = new Demo();

console.log(demo);  // Demo {0: 1, 1: 2, 2: 3, 3: 4, 4: 5}

But How can i defined like this in Typescript

Can't access them in ts

typescript error:

Property '0' does not exist on type 'Demo'. (2339)

Answer 1

You can extend the Array object:

class Demo extends Array<number> {
    constructor() {
        super();

        [1, 2, 3, 4, 5].forEach(v => this.push(v))
    }
}

let a = new Demo();
console.log(a[0]); // 1
a.forEach(item => console.log(item));

( code in playground )