Seeing the difference between using await with Array.prototype.forEach and using await with for...of.

await-for-each.js

function testForEachReplies(maxSecs = 4) {
  async function replyIn(secs) {
    return await {
      then(res, rej) {
        setTimeout(
          _ => res(`I replied after ${secs} second${secs - 1 ? 's' : ''}`),
          secs * 1e3
        );
      }
    };
  }

  let replies = [];
  for (let i = 1; i <= maxSecs; i++) {
    replies.push(replyIn(i));
    for (let j = 1; j < i; j++) {
      replies.push(replyIn(j));
    }
  }

  console.log((new Date).toJSON());
  replies.forEach(async function (reply) {
    console.log(await reply);
  });
  console.log((new Date).toJSON());
}

testForEachReplies();

await-for-of.js

async function testForOfReplies(maxSecs = 4) {
  async function replyIn(secs) {
    return await {
      then(res, rej) {
        setTimeout(
          _ => res(`I replied after ${secs} second${secs - 1 ? 's' : ''}`),
          secs * 1e3
        );
      }
    };
  }

  let replies = [];
  for (let i = 1; i <= maxSecs; i++) {
    replies.push(replyIn(i));
    for (let j = 1; j < i; j++) {
      replies.push(replyIn(j));
    }
  }

  console.log((new Date).toJSON());
  for (let reply of replies) {
    console.log(await reply);
  }
  console.log((new Date).toJSON());
}

await testForOfReplies();

~README.md

The main difference seems to be that due to the fact that you must iterate through the await responses using an async function in the forEach version, the replies actually appear out of order.