使用for循环时如何将值传递回生成器函数

Question

I'm learning about generators and and iterators and I can't figure out, nor find any details on how to pass a value back to a generator object when iterating over the object using a for of loop. I'd like to pass the counter value back on each iteration. How is this possible?

function generate(time, id) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log(`ALERT: ${id}`)
      resolve(`${id} success.`)
    }, time)
  })
}

function* generator() {
  const testA = yield generate(3000, 'A')
  console.log(`Returned: ${testA}`)
  const testB = yield generate(500, 'B')
  console.log(`Returned: ${testB}`)
  const testC = yield generate(300, 'C')
  console.log(`Returned: ${testC}`)
}

async function test() {
  let counter = 1
  const genObj = generator()
  // await genObj.next(counter).value
  // counter += 1
  // await genObj.next(counter).value
  for (x of genObj) {
    console.log('From here.')
    const t = await x
    counter += 1
    console.log(t)
  }
}

test()

Answer 1

By the spec this is not possible as no arguments are passed to the next() method internally when used in iterator loops like for ... of

https://www.ecma-international.org/ecma-262/6.0/#sec-iterator-interface

The for-of statement and other common users of Iterators do not pass any arguments, so Iterator objects that expect to be used in such a manner must be prepared to deal with being called with no arguments.

So in your case you would have to do a loop where you explicitly call next()