As others have mentioned; if you aren’t using Promise.all, you are likely missing a good deal of opportunities for easier and more performant async code.
The "inner workings" could be a for loop, with the exception of rejected promises. The only opportunity for quicker resolution is when one of the promises reject, at which time Promise.all() immediately rejects.
I think the allegations of "easier" are significantly overblown too.
// A -- Async and parallel
const results = await Promise.all(data.map((i) => delay(i)));
// B -- Functionally equivalent to the above
const promises = data.map((i) => delay(i));
const result = [];
for (let a of promises) {
const r = await a;
result.push(r);
}
// C -- Problematic and naive approach: much slower
const result = [];
for (let i of data) {
const r = await delay(i);
result.push(r);
}