For..of with Symbol.asyncIterator

Question

Why Symbol.asyncIterator is not working?

const obj = {
  async *[Symbol.asyncIterator] () {
    yield 10;
    yield 100;
    yield 1000;
  },
};

for (const val of obj) {
  console.log(obj);
}

error: TypeError: obj is not iterable

for await (const val of obj) {
  console.log(obj);
}

error: SyntaxError: for await (... of...) is only valid in async functions and async generators

(async() => {
  for await (const val of obj) {
    console.log(val);
  }
})()

error: SyntaxError: for await (... of...) is only valid in async functions and async generators

Answer 1

Because it's an async iterable, you need to await each value:

for await (const val of obj) {
  console.log(obj);
}

NOTE: this all needs to be wrapped in an async function because Node.js doesn't support top-level await by default:

(async() => {
  for await (const val of obj) {
    console.log(val);
  }
})()

Answer 2

Use await in an async function

 const obj = { async * [Symbol.asyncIterator]() { yield 10; yield 100; yield 1000; }, }; (async() => { for await (const val of obj) { console.log(val); } })()