JavaScript

Promises.allSettled() in JavaScript

🔍 What is Promise.allSettled()?

Promise.allSettled() takes an array of promises and returns a new promise that resolves after all of them settle (either fulfilled or rejected). Unlike Promise.all(), it never short-circuits and gives you the result of each promise.

>>“Give me the full report — successes and failures alike.”

📦 Syntax

Code Snippet

Promise.allSettled([promise1, promise2, promise3])
  .then((results) => {
    results.forEach((result) => {
      if (result.status === "fulfilled") {
        console.log("✅", result.value);
      } else {
        console.log("❌", result.reason);
      }
    });
  });

🚀 Example

Mix of Fulfilled and Rejected

const p1 = Promise.resolve("✅ Success A");
const p2 = Promise.reject("❌ Error B");
const p3 = Promise.resolve("✅ Success C");

Promise.allSettled([p1, p2, p3])
  .then((results) => {
    results.forEach((result, i) => {
      console.log(`Promise ${i + 1}:`, result);
    });
  });

Note

💡 Each result is an object with a status of either "fulfilled" or "rejected", and includes either a value or a reason.

📋 Output Structure

Sample Output

[
  { status: "fulfilled", value: "✅ Success A" },
  { status: "rejected", reason: "❌ Error B" },
  { status: "fulfilled", value: "✅ Success C" }
]

💼 Use Case: Logging Results Regardless of Success

Promise.allSettled() is great when you want to wait for all tasks to finish but don’t want a single failure to interrupt the rest.

Useful for Multiple API Results

const urls = ["api/a", "api/b", "api/c"];
const requests = urls.map((url) => fetch(url));

Promise.allSettled(requests).then((results) => {
  results.forEach((result, index) => {
    if (result.status === "fulfilled") {
      console.log(`✅ API ${index + 1} success:`, result.value);
    } else {
      console.warn(`❌ API ${index + 1} failed:`, result.reason);
    }
  });
});

🧠 Key Points

Waits for all promises to settle — no short-circuiting.
Returns a result object for every promise, whether fulfilled or rejected.
Useful for bulk operations, logging, and fault-tolerant systems.

📚 References

>>“When you care about what happened to everything — not just who won.”