Performances

A little point about performances .

looping on decisions can be time consuming, and will block the event loop . So, we choose to be slower, but to unblock the event loop .

Examples

Here is an example :

// example 1 a promise containing a loop
const fn = async () => {
  console.log('start loop');
  console.time('loop');
  for (let i = 0; i < 1e5; i++) {
  }
  console.timeEnd('loop');
}

// we don't await fn
fn();
console.log('do other things');

will log :

start loop
loop: 0.779052734375 ms
do other things

your node app is totally blocked waiting the loop to end

here is another example :

// example 2 a promise containing a loop, calling setImmediate

const fn = async () => {
  console.log('start loop');
  console.time('loop');
  for (let i = 0; i < 1e5; i++) {
    await setImmediatePromise();
  }
  console.timeEnd('loop');
}

//just to call setImmediate in async context
const setImmediatePromise = () => {
    return new Promise<void>((resolve) => {
        setImmediate(() => resolve());
    });
};

// we don't await fn
fn();
console.log('do other things');

will log :

start loop
do other things
loop: 5852.944091796875 ms

yesn the loop is much slower ... but, it doesn't froze your app, and you can do other async things