Await vs Promise.all concurrency comparison

await-vs-promise-all-concurrency.js

async function runTask(seconds, msg) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(`RESULT: ${msg}`);
    }, seconds * 1000);
  });
}

async function testPromiseAll() {
  return Promise.all([
    runTask(2, 'Promise first'),
    runTask(1, 'Promise second'),
    runTask(3, 'Promise third'),
    runTask(1, 'Promise fourth'),
  ]);
}

async function testMultipleAwaits() {
  const result1 = await runTask(2, 'await first');
  const result2 = await runTask(1, 'await second');
  const result3 = await runTask(3, 'await third');
  const result4 = await runTask(1, 'await fourth');
  return [ result1, result2, result3, result4 ];
}

async function runTest(fn) {
  const label = fn.name;
  console.time(label);
  const results = await fn();
  console.timeEnd(label);
  console.log(`${label} results`, results);
}

async function runTests() {
  return Promise.all([
    runTest(testPromiseAll),
    runTest(testMultipleAwaits)
  ]);
}

function main() {
  runTests();
}

main();

Running the above produces the following output:

testPromiseAll: 3.005s
MAIN: resultPromise [
  'RESULT: Promise first',
  'RESULT: Promise second',
  'RESULT: Promise third',
  'RESULT: Promise fourth'
]
testMultipleAwaits: 7.005s
MAIN: resultAwait [
  'RESULT: await first',
  'RESULT: await second',
  'RESULT: await third',
  'RESULT: await fourth'
]