Custom async iterator

async-iterator.js

let range = {
  from: 1,
  to: 5,

  [Symbol.asyncIterator]() {
    return {
      current: this.from,
      last: this.to,

      async next() {
        await new Promise(resolve => setTimeout(resolve, 1000))

        if (this.current <= this.last) {
          return { done: false, value: this.current++ }
        } else {
          return { done: true }
        }
      }
    }
  }
}

(async () => {
  for await (let value of range) {
    console.log(value)
  }
})