Generators

id-generator.js

function* IdGenerator() {
  let id = 0;
  while (true) {
    yield ++id;
  }
}

const idIterator = IdGenerator();

const ninja1 = { id: idIterator.next().value };
const ninja2 = { id: idIterator.next().value };
const ninja3 = { id: idIterator.next().value };

console.log(ninja1.id === 1, 'First ninja has id 1');
console.log(ninja2.id === 2, 'Second ninja has id 2');
console.log(ninja3.id === 3, 'Third ninja has id 3');

weapon-generator-1.js

function* WeaponGenerator() {
  yield 'Katana';
  yield 'Wakizashi';
  yield 'Kusarigama';
}

for (let weapon of WeaponGenerator()) {
  console.log(weapon !== undefined, weapon);
}

weapon-generator-2.js

function* WeaponGenerator() {
  yield 'Katana';
  yield 'Wakizashi';
}

const weaponsIterator = WeaponGenerator();

const result1 = weaponsIterator.next();
console.log(
  typeof result1 === 'object' && result1.value === 'Katana' && !result1.done,
  'Katana received!'
);

const result2 = weaponsIterator.next();
console.log(
  typeof result2 === 'object' && result2.value === 'Wakizashi' && !result2.done,
  'Wakizashi received!'
);

const result3 = weaponsIterator.next();
console.log(
  typeof result3 === 'object' && result3.value === undefined && result3.done,
  'There are no more results!'
);

weapon-generator-3.js

function* WeaponGenerator() {
  yield 'Katana';
  yield 'Wakizashi';
}

const weaponsIterator = WeaponGenerator();
var item;
while (!(item = weaponsIterator.next()).done) {
  console.log(item !== null, item.value);
}

weapon-generator-4.js

function* WarriorGenerator() {
  yield 'Sun Tzu';
  yield* NinjaGenerator();
  yield 'Genghis Khan';
}

function* NinjaGenerator() {
  yield 'Hatori';
  yield 'Yoshi';
}

for (let warrior of WarriorGenerator()) {
  console.log(warrior !== null, warrior);
}