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User defined Iterables

As a generator function returns an iterator, you can conveniently define the [Symbol.iterator] method as a generator function instead.


class AnimalsList {
  constructor(...args) {
    this.index = -1;
    this.animals = args;
  }

  *[Symbol.iterator]() {
    while (this.index < this.animals.length - 1) {
      this.index++;
      yield this.animals[this.index];
    }
  }
}

var myAnimals = new AnimalsList('Brownie', 'Greenie', 'Lucky', 'Spotty');
for (let v of myAnimals) console.log(v);

Brownie Greenie Lucky Spotty

At the time of writing, Array.prototype.values() is not supported by browsers. In the future, you may do the following instead:


class AnimalsList {
  constructor(...args) {
    this.animals = args;
  }

  *[Symbol.iterator]() {
    return this.animals.values();
  }
}