Wait For Multiple Promises To Finish

Have you ever encountered a situation where you needed to wait for multiple promises to finish in your code? Juggling asynchronous tasks can be tricky, but fear not! In this article, we will walk you through a helpful approach to manage multiple promises in JavaScript and ensure they all complete before proceeding.

So, what are promises in JavaScript? Promises are objects that represent the eventual completion or failure of an asynchronous operation and its resulting value. They are a fundamental part of handling asynchronous operations in JavaScript and are widely used in modern web development.

When you need to wait for multiple promises to complete before performing some action, you can use the `Promise.all()` method. This method takes an iterable of promises as an input and returns a single Promise that resolves when all of the input promises have resolved, or rejects with the reason of the first promise that rejects.

Here's an example of how you can use `Promise.all()` to wait for multiple promises to finish:

const promise1 = fetch('https://api.example.com/data1');
const promise2 = fetch('https://api.example.com/data2');
const promise3 = fetch('https://api.example.com/data3');

Promise.all([promise1, promise2, promise3])
  .then((responses) => {
    // All promises have resolved successfully
    console.log('All promises have been fulfilled:', responses);
    // Proceed with further actions here
  })
  .catch((error) => {
    // Something went wrong with one of the promises
    console.error('An error occurred while waiting for promises:', error);
  });

In this example, we create three fetch requests that return promises for fetching data from different URLs. We then use `Promise.all()` to wait for all three promises to resolve. Once all promises are fulfilled, the `.then()` callback will execute, allowing you to handle the results of all promises together.

Remember, if any of the promises in the iterable rejects, the `Promise.all()` method's returned promise will be rejected with the reason from the first promise that was rejected. This behavior can be useful for error handling and ensuring robustness in your asynchronous code.

Additionally, you can combine `Promise.all()` with the `async/await` syntax for more concise and readable code. Here's an example using `async/await`:

async function fetchData() {
  try {
    const [data1, data2, data3] = await Promise.all([
      fetch('https://api.example.com/data1'),
      fetch('https://api.example.com/data2'),
      fetch('https://api.example.com/data3')
    ]);
    console.log('All data fetched successfully:', data1, data2, data3);
    // Continue with further processing
  } catch (error) {
    console.error('An error occurred while waiting for data:', error);
  }
}

fetchData();

By using `async/await` with `Promise.all()`, you can achieve the same result in a more synchronous-looking and clean manner.

In conclusion, managing multiple promises in JavaScript can be made simple and efficient by using `Promise.all()`. This technique allows you to wait for all promises to finish before proceeding with your code logic. Whether you prefer the traditional `.then().catch()` syntax or the modern `async/await` approach, mastering the handling of multiple promises will level up your asynchronous coding skills. Happy coding!