How do you implement a custom Promise.all with error handling?

Question

Accepted Answer

**Custom Promise.all** — handle mixed results and errors.

```javascript
async function promiseAllSettled(promises) {
    return Promise.all(
        promises.map(promise =>
            promise
                .then(value => ({ status: "fulfilled", value }))
                .catch(reason => ({ status: "rejected", reason }))
        )
    );
}

// Usage
const results = await promiseAllSettled([
    fetch("https://api1.com/data"),
    fetch("https://api2.com/data"),
    fetch("https://api3.com/data"),
]);

results.forEach(result => {
    if (result.status === "fulfilled") {
        console.log("Success:", result.value);
    } else {
        console.error("Failed:", result.reason);
    }
});

// With concurrency limit
async function promiseAllWithLimit(promises, limit) {
    const results = [];
    const executing = new Set();

for (const [i, promise] of promises.entries()) {
        const p = promise.then(result => {
            results[i] = { status: "fulfilled", value: result };
            executing.delete(p);
        }).catch(err => {
            results[i] = { status: "rejected", reason: err };
            executing.delete(p);
        });

executing.add(p);

if (executing.size >= limit) {
            await Promise.race(executing);
        }
    }

await Promise.all(executing);
    return results;
}
```

Node.js: How do you implement a custom Promise.all with error handling?