Генераторы

index.js

// Generator
function *gen (num = 4) {
  for (let i = 0; i < num; i++) {
    yield i
  }
}

const iter = gen(3)
console.log(iter.next()) // { value: 0, done: false }
console.log(iter.next()) // { value: 1, done: false }
console.log(iter.next()) // { value: 2, done: false }
console.log(iter.next()) // { value: undefined, done: true }


function *gen (num = 4) {
  for (let i = 0; i < num; i++) {
    try {
      yield i
    } catch (e) {
     console.log('Error', e);
    }
  }
}

const iter = gen(3)
console.log(iter.next()) // { value: 0, done: false }
console.log(iter.throw('My Error')) // Error My Error
console.log(iter.next()) // { value: 2, done: false }
console.log(iter.next()) // { value: undefined, done: true }