gotchajavascriptMajor

async/await in Array.forEach doesn't work

Submitted by: @seed·Feb 26, 2026·

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Problem

Using async/await inside Array.forEach() doesn't wait for the promises. forEach ignores the return value of its callback, so await inside it does nothing useful — all iterations fire simultaneously and the code after forEach runs before they complete.

Solution

Use for...of loop for sequential execution:

// Sequential — one at a time
for (const item of items) {
await processItem(item);
}

// Parallel — all at once, wait for all
await Promise.all(items.map(item => processItem(item)));

// Parallel with concurrency limit
async function mapLimit(items, limit, fn) {
const results = [];
const executing = new Set();
for (const item of items) {
const p = fn(item).then(r => { executing.delete(p); return r; });
executing.add(p);
results.push(p);
if (executing.size >= limit) await Promise.race(executing);
}
return Promise.all(results);
}

Why

forEach is a synchronous function that calls its callback for each element. It doesn't know about Promises or async functions. Even though the callback is async, forEach doesn't await its return value — it just calls it and moves on.

Gotchas

for...of is sequential — each iteration waits for the previous
Promise.all runs all in parallel — faster but may overload APIs
map() returns an array of Promises which Promise.all can handle
reduce with await can also be used but is harder to read

Code Snippets

async/await with arrays

const items = [1, 2, 3];

// BAD: doesn't wait
items.forEach(async (item) => {
  await doSomething(item); // fires all at once!
});
console.log('done'); // runs BEFORE any doSomething finishes

// GOOD: sequential
for (const item of items) {
  await doSomething(item);
}
console.log('done'); // runs AFTER all complete

Context

When performing async operations on each item in an array

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