JAVASCRIPT

initializing a property asynchronously

class DataContainer {
  #data; // (A)
  constructor() {
    Promise.resolve('downloaded')
      .then(data => this.#data = data); // (B)
  }
  getData() {
    return 'DATA: '+this.#data; // (C)
  }
}

initializing a property asynchronously 2

const dc = new DataContainer();
assert.equal(dc.getData(), 'DATA: undefined');
setTimeout(() => assert.equal(
  dc.getData(), 'DATA: downloaded'), 0);