Promise.any: Examples and Use Cases in JavaScript

Promise.any: Examples and Use Cases in JavaScript

Promise.any returns as soon as the first promise fulfills. It ignores rejections until all reject. Here are practical examples.

First Successful Source

const fastest = await Promise.any([
  fetchFromCDN(),
  fetchFromOrigin(),
  fetchFromMirror(),
]);
``
Use whichever source succeeds first. If all fail, it rejects with `AggregateError`.

### Best Effort with Fallback

```js
try {
  const result = await Promise.any([
    primaryAPI(),
    secondaryAPI(),
    tertiaryAPI(),
  ]);
  render(result);
} catch (err) {
  console.error("All APIs failed:", err.errors); // AggregateError
  render(fallbackData);
}
``
### AggregateError

If all promises reject, `Promise.any` rejects with an `AggregateError`:

```js
try {
  await Promise.any([
    Promise.reject(new Error("A failed")),
    Promise.reject(new Error("B failed")),
  ]);
} catch (err) {
  console.error(err instanceof AggregateError); // true
  console.error(err.errors); // [Error: A failed, Error: B failed]
}
``
`err.errors` is an array of all the individual rejection reasons.

### Difference from Promise.race

```js
// race: first to settle (can be a rejection)
const r = await Promise.race([Promise.reject("err"), Promise.resolve("ok")]);
// could throw "err" or return "ok", depending on which settles first

// any: first to fulfill (ignores rejections)
const a = await Promise.any([Promise.reject("err"), Promise.resolve("ok")]);
// returns "ok" (ignores the rejection)
``
### Empty Array

```js
const result = await Promise.any([]); // rejects with AggregateError (all reject)
``
`Promise.any([])` rejects immediately with an `AggregateError` (no promises to fulfill).

### The Takeaway

`Promise.any` returns the first promise to fulfill. It ignores rejections until all reject. Use for first successful source and best-effort with fallback. If all reject, it throws `AggregateError` with `errors` array. Different from `race` (which returns the first to settle, even a rejection).