How to Fix Promise Allsettled Error in Node.js

Stumbled on a promise allsettled error in your Node.js application? This common issue has a well-known fix that you can apply in minutes.

The Problem

Promise.allSettled() was introduced in ES2020. If your Node.js application targets older Node.js versions (below 12.9) or uses a bundler configuration that doesn't include the necessary polyfills, you'll encounter a TypeError: Promise.allSettled is not a function at runtime.

How to Fix It

The best approach is to upgrade your Node.js version. If that's not possible, add a polyfill:

// Option 1: Polyfill for older environments
if (!Promise.allSettled) {
  Promise.allSettled = (promises) =>
    Promise.all(
      promises.map((p) =>
        Promise.resolve(p)
          .then((value) => ({ status: "fulfilled", value }))
          .catch((reason) => ({ status: "rejected", reason }))
      )
    );
}

// Option 2: Use it with proper error handling
const results = await Promise.allSettled([
  fetchUsers(),
  fetchOrders(),
  fetchProducts(),
]);

const fulfilled = results.filter((r) => r.status === "fulfilled");
const rejected = results.filter((r) => r.status === "rejected");

if (rejected.length > 0) {
  console.warn("Some requests failed:", rejected.map(r => r.reason));
}

// Process successful results
const data = fulfilled.map((r) => r.value);

When to Use allSettled vs all

• `Promise.all` fails fast on the first rejection — use when all promises must succeed
• `Promise.allSettled` waits for everything and reports each result individually — use when you want partial results even if some promises fail

Node.js Version Check

Run node --version to verify your runtime. Version 12.9.0+ supports allSettled natively. For production, targeting Node 16+ or 18+ is recommended.

Track unhandled promise rejections and allSettled failures automatically with [Bugsly](https://bugsly.dev) — get full stack traces for every rejected promise in your Node.js app.