As a developer, you may want to perform asynchronous programming to optimize time and make your application more effective. JavaScript Promises is a simple yet powerful tool that can help you manage asynchronous requests and processes.

What are JavaScript Promises?

Promises are a concept introduced in JavaScript to make asynchronous operations easier and clearer. A promise is essentially an object that represents the future completion of an asynchronous operation. A promise has three states: Pending, Fulfilled, and Rejected. When the promise is fulfilled, it returns the result generated during the asynchronous operation. When it is rejected, it returns the error that occurred during the asynchronous operation.

How to Use JavaScript Promises?

Using Promises in JavaScript is relatively easy. You can create a Promise object by calling the Promise class and passing a function with an asynchronous operation as an argument. The asynchronous operation can be an AJAX call or an asynchronous function that returns another Promise.

const myPromise = new Promise((resolve, reject) => {
  // An asynchronous operation is performed here
  if (/* condition met */) {
    resolve(/* success result */);
  } else {
    reject(/* error result */);
  }
});

myPromise.then((result) => {
  // The result is processed here
}).catch((error) => {
  // The error is processed here
});

JavaScript Promises vs. Async/Await

Async/Await is another technique used in JavaScript to manage asynchronous operations. Unlike Promises, Async/Await provides a syntactic sugar function that allows developers to write asynchronous operations like synchronous code.

async function myAsyncFunction() {
  try {
    const result = await myPromise;
    // The result is processed here
  } catch (error) {
    // The error is processed here
  }
}

Another important difference between Promises and Async/Await is that Promises can execute multiple operations simultaneously, while Async/Await can only execute one operation at a time.

When to Use Promises vs. Async/Await?

Promises should be used e.g. when multiple asynchronous operations need to be executed simultaneously. On the other hand, Async/Await is typically enough when there is only one asynchronous operation that needs to be executed.

// Promises
Promise.all([
  asyncOperation1(),
  asyncOperation2(),
  asyncOperation3()
]).then((results) => {
  // All results are processed here
}).catch((error) => {
  // The error is processed here
});

// Async/Await
async function myAsyncFunction() {
  try {
    const result1 = await asyncOperation1();
    const result2 = await asyncOperation2();
    const result3 = await asyncOperation3();
    // All results are processed here
  } catch (error) {
    // The error is processed here
  }
}

In the code snippet above, you can see the usage of Promise.all. This is a useful function that allows developers to execute multiple Promises simultaneously and wait for their results. Promise.all returns a new Promise that is fulfilled only when all Promises are completed. If at least one Promise is rejected, Promise.all returns the error of the rejected Promise.

TL;DR

In conclusion, JavaScript Promises is a powerful tool that simplifies asynchronous programming. It allows developers to manage multiple asynchronous operations and handle errors effectively. Async/Await is another technique that provides syntactic sugar for writing asynchronous code but is best suited for handling single operations. Promise.all is a useful function that executes multiple Promises simultaneously and waits for their results. By using Promises, developers can make their code more efficient, readable, and easier to maintain.