What is the purpose of a Promise in JavaScript?

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The purpose of a Promise in JavaScript is to handle asynchronous operations in a more manageable and readable way, avoiding deeply nested callbacks (known as "callback hell"). A Promise represents a value that may be available now, in the future, or never. It acts as a placeholder for a result that is initially unknown but will be resolved eventually.

A Promise has three states:

1. Pending – the initial state, before the result is known.

2. Fulfilled – the operation completed successfully, and a resulting value is available.

3. Rejected – the operation failed, and an error reason is available.

Promises provide two main methods:

• .then(onFulfilled) – runs when the Promise is fulfilled.

• .catch(onRejected) – runs if the Promise is rejected.

This allows developers to chain asynchronous steps in a clear sequence, making the code easier to read and maintain.

In this example, each step waits for the previous one to complete, and any errors are caught in one place. Promises are essential for handling tasks like API calls, file operations, and timers, where results aren't immediately available but need to be handled once they are. They form the foundation for async/await syntax introduced in ES2017.

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