The for-await-of syntax is similar to the for-of iteration. The key difference is that it automatically awaits any promises generated by the iterator. This lesson covers how to consume async data sources easily with for-await-of.

for-await-of essentially allows you to use async/await in a generator function.

 

import { magic } from './server';(Symbol as any).asyncIterator =  (Symbol as any).asyncIterator  || Symbol.for("Symbol.asyncIterator");async function* numbers() {  let index = 1;  while (true) {    yield index;    index = await magic(index);    if (index > 10) {      break;    }  }}async function main() {  for await (const num of numbers()) {    console.log(num);  }}main();

 

Server:

const magic = (i: number) => new Promise
     
      (res => setTimeout(res(i + 1), 100));
     

 

Example 2:

// Asynchronous generatorsasync function asyncGenerators () {    async function* createAsyncIterable(syncIterable) {        for (const elem of syncIterable) {            yield elem;        }    }        const asyncGenObj = createAsyncIterable(['a', 'b']);    const [{value:v1}, {value:v2}] = await Promise.all([        asyncGenObj.next(), asyncGenObj.next()    ]);    console.log("v1", v1, "v2", v2); // a, b}asyncGenerators();