Recently, I was working on a project that required me to make multiple API requests simultaneously. I was worried about how to carry out these requests without breaking other things. I started looking for ways to achieve my goal, and I remembered using the JavaScript promise.all() method a few years ago. I went back to the project, and it made sense. I started to do more research on it, and I was able to make multiple requests using the method.

This is why I am writing this article as a guide for unlocking the unlimited abilities of promise.all().

What is promise.all()?

promise.all() is a JavaScript method that takes an iterable of promises as input and returns a single promise that resolves when all of the input promises resolve. If any of the input promises reject, the promise.all() promise will also reject.

Imagine you have five friends, and each friend has a special toy that you want to play with. But here's the catch: your friends live far away, and you can't visit them all at once. You have to wait for each friend to send their toy to you through the mail.

Now, waiting for one friend's toy to arrive is not too bad, but waiting for all five toys to arrive can take a long time. You might get bored and want to do something else while you wait.

Here's where Promise.all() comes in! It's like having a superpower that lets you ask all your friends to send their toys at the same time, and you can do other things while you wait.

With Promise.all(), you create a special promise for each friend's toy and put them all together. Then you tell Promise.all() to wait for all the promises to be fulfilled, meaning that all the toys have arrived.

Once all the promises are fulfilled, Promise.all() will let you know, and you can start playing with all the toys at once! This way, you don't have to wait for each toy to arrive separately, and you can have lots of fun without getting bored.

So, Promise.all() is like a magic spell that helps you handle multiple things happening at the same time, like waiting for toys to arrive from your friends. It makes your code more efficient and lets you do other things while you're waiting for everything to finish.

How to use promise.all()

To use promise.all(), you first need to create an iterable of promises. You can do this by using the Promise.resolve() method to create a promise that resolves immediately, or by using the fetch() method to make an asynchronous request.

Once you have created an iterable of promises, you can pass it to the promise.all() method. The promise.all() method will then return a single promise that resolves when all of the input promises resolve.

Examples

The following code shows how to use promise.all() to make two asynchronous requests and then print the results:

// Example 1: Make two asynchronous requests and print the results
const promise1 = Promise.resolve(“Hello”); const promise2 = fetch(“https://example.com");

const promises = [promise1, promise2];

const allPromises = Promise.all(promises);

allPromises.then(results => { console.log(results); });

// Example 2: Make three asynchronous requests and print the results
const promise1 = Promise.resolve(“Hello”); const promise2 = fetch(“https://example.com"); const;const) promise3 = fetch(“https://example.com/api/users");

const promises = [promise1, promise2, promise3];

const allPromises = Promise.all(promises);

allPromises.then(results => { console.log(results); });

// Example 3: Make an asynchronous request and then do something with the result
const promise = fetch(“https://example.com");

promise.then(response => { // Do something with the response });

// Example 4: Make an asynchronous request and then handle errors gracefully const promise = fetch(“https://example.com");

promise.then(response => { // Do something with the response }, error => { // Handle the error });

In this example 1, the promise1 promise resolves immediately with the string "Hello". The promise2 promise makes an asynchronous request to the URL https://example.com.

The promise.all() method will then wait for both promises to resolve before returning a single promise. The allPromises promise will then resolve with an array containing the results of both promises.

The allPromises promise is then used to print the results of both promises.

Benefits of using promise.all()

There are several benefits to using promise.all():

• It can help to improve the performance of your code by reducing the number of asynchronous requests that need to be made.

• It can help to simplify your code by reducing the need to write nested then() callbacks.

• It can help to make your code more robust by handling errors gracefully.

If you are working on a project that requires you to make multiple asynchronous requests, I encourage you to use promise.all(). It is a powerful tool that can help you to improve the performance, simplicity, and robustness of your code.