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What is a JavaScript Promise?

In JavaScript, a promise is an object that represents the eventual completion or failure of an asynchronous operation. Promises are a key feature in modern web development, aiding in the management of asynchronous actions. They provide a cleaner alternative to the traditional callback-based approach.

Promise States

• Pending: The initial state, neither fulfilled nor rejected.
• Fulfilled: The operation completed successfully, and the promise has a resultant value.
• Rejected: The operation failed, and the promise has a reason for the failure (an error).

Creating a Promise

A promise is created using the Promise constructor, which takes a single function as an argument. This function, known as the executor, receives two parameters: resolve and reject.

const myPromise = new Promise((resolve, reject) => {
        // Async operation here
        if (/* success condition */) {
            resolve('Success!');
        } else {
            reject('Failure!');
        }
    });

Using Promises

Once a promise is created, you can use the .then() method to handle success and .catch() to handle failure. For example:

myPromise
        .then(result => console.log(result))
        .catch(error => console.error(error));

In summary, JavaScript promises significantly enhance asynchronous programming, making code easier to read and maintain.