class Data {
  public get values(): Array<number> {
    // Return a defensive copy of the array
    return Object.assign([], this._values);
  }
  private readonly _values: Array<number>;
  constructor(size: number) {
    this._values = Array(size);
  }
  private setValueAtIndex(index: number, value) {
    if (index < 0 || index + 1 > this._values.length) {
      throw new Error('Invalid index');
    } else if (value < 0) {
      throw new Error('Value should be positive');
    }
  }
}

const data = new Data(3);
const values = data.values;
values[0] = -10;
console.log(`array inside data object: ${data.values}`);