JavaScript Promises are a fundamental concept for handling asynchronous operations. They allow developers to write cleaner and more manageable code when dealing with tasks like API calls, file operations, or timers.

Key Concepts of Promises

  1. States
    A Promise can be in one of three states:

    • Pending (initial state)
    • Fulfilled (success)
    • Rejected (failure)
    Promise_Status

  2. Syntax 

    const promise = new Promise((resolve, reject) => {
  // Asynchronous operation
  if (success) {
    resolve(value);
  } else {
    reject(error);
  }
});

  3. Chaining
    Use .then() for success and .catch() for errors: 

    promise.then(result => {
  // Handle fulfilled
}).catch(error => {
  // Handle rejected
});
    Promise_Chain

Best Practices

  • Always use .catch() to handle errors in chains.
  • Avoid .then() without a handler to prevent unhandled rejections.
  • Combine Promises with async/await for simpler flow control.

For deeper insights into asynchronous functions, visit our JavaScript Async Functions guide.

Promise_Basics

Explore more examples and use cases in the JavaScript Promises section.