Run results for: Await vs Then

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser: Chrome 121

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 2 years ago

Benchmark engine: Benchmark.js

Then

4.9M/s

Await

4.0M/s

View exact numbers

Test name	Executions per second
✓ Then	4,868,605 Ops/sec
Await	3,965,900 Ops/sec

Script Preparation code:

function foo(i) {
  return Promise.resolve(i+1);
}

function recur(i) {
  return i >= 10 ? Promise.resolve(i) : foo(i).then(recur);
}

function testThen() {
  return foo(0).then(recur);
}

async function testAwait() {
  let i = await foo(0);
  while (i < 10) {
    i = await foo(i);
  }
  
  return i;
}

Tests:

Then
testThen()
Await
testAwait();