Exploring The Difference Between Async/Await and Promises in JavaScript

why and how ?


In JavaScript, asynchronous programming is essential for handling tasks that may take some time to complete, such as fetching data from an API or reading a file. Two common ways to work with asynchronous code in JavaScript are Promises and the newer Async/Await syntax. In this article, we will explore the differences between Async/Await and Promises, and when to use each approach.

Promises in JavaScript:

Promises were introduced in ES6 as a way to handle asynchronous operations more elegantly than callbacks. A Promise represents a value that may be available now, or in the future, or never. Promises have three states: pending, fulfilled, or rejected. They allow you to chain multiple asynchronous operations together using the then method.

  • Promises serve as objects that symbolize the eventual completion or failure of asynchronous tasks.
  • They exist in three states: pending, fulfilled, or rejected.
  • Promise syntax revolves around the sequential chaining of .then()​ and .catch()​ methods to manage asynchronous outcomes and errors.
  • Compared to traditional callback-based approaches, promises offer enhanced error management capabilities.
// Example function returning a promise
function fetchData() {
    return new Promise((resolve, reject) => {
        // Simulating asynchronous task
        setTimeout(() => {
            const data = 'Resolved data';
            // Resolving promise with data
            // Rejecting promise with error
            // reject(new Error('Failed to fetch data'));
        }, 2000);

// Consuming the promise using .then() and .catch() methods
    .then(data => {
        console.log('Data fetched successfully:', data);
    .catch(error => {
        console.error('Error fetching data:', error);

Async/Await in JavaScript:

Async/Await is a more recent addition to JavaScript, introduced in ES8. It provides a more concise and readable way to write asynchronous code compared to Promises. Async functions are declared with the async keyword, and within an async function, you can use the await keyword to pause the execution of the function until a Promise is resolved.

  • Async functions introduce a more intuitive approach to writing asynchronous code by permitting the usage of the await keyword within them.
  • Async/await syntax enables developers to craft asynchronous code in a manner akin to synchronous programming, thereby enhancing code readability.
  • Async functions inherently return promises, streamlining the chaining of asynchronous operations.
  • Error handling in async/await is simplified through the integration of try-catch blocks, resulting in more concise and comprehensible code.
  • An example code snippet demonstrates the application of async/await for managing asynchronous tasks.
// Example async function using await
async function fetchDataAsync() {
    try {
        // Using await to asynchronously wait for the promise to resolve
        const data = await fetchData();
        console.log('Data fetched successfully:', data);
    } catch (error) {
        console.error('Error fetching data:', error);

// Invoking the async function

Differences Between Async/Await and Promises:

  1. Syntax: Async/Await provides a more synchronous-looking syntax compared to Promises, making the code easier to read and understand.
  2. Error Handling: With Promises, you handle errors using the catch method, while with Async/Await, you can use try/catch blocks for error handling, which can make error handling more straightforward.
  3. Chaining: Promises are chained using the then method, while Async/Await allows you to write asynchronous code in a more linear fashion without nested callbacks.
  4. Readability: Async/Await code tends to be more readable and maintainable compared to Promise chains, especially for complex asynchronous operations.

When to Use Promises:

  • If you are working with existing code that uses Promises.
  • When you need more control over the flow of asynchronous operations.
  • When you need to work with libraries or APIs that return Promises.

When to Use Async/Await:

  • For writing new asynchronous code, especially for readability and maintainability.
  • When you need to handle errors more effectively.
  • When you want to avoid callback hell and write asynchronous code in a more synchronous style.


In conclusion, both Promises and Async/Await are powerful tools for handling asynchronous operations in JavaScript. Promises provide a more traditional way of working with asynchronous code, while Async/Await offers a more modern and readable approach. Understanding the differences between the two and knowing when to use each can help you write more efficient and maintainable JavaScript code.

Exploring  The Difference Between Async/Await and Promises in JavaScript
Ram Krishna April 8, 2024
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