What are Promises in JavaScript?

Promises are a key feature in JavaScript that help manage asynchronous operations. They represent a value that may be available now, or in the future, or never. Promises allow developers to write asynchronous code in a more readable and manageable way, avoiding the dreaded "callback hell."

Key Concepts of Promises:

1. States of a Promise:

- Pending: Initial state, neither fulfilled nor rejected.

- Fulfilled: Operation completed successfully.

- Rejected: Operation failed.

2. Creating a Promise:

   javascript
   let promise = new Promise((resolve, reject) => {
       // Some asynchronous operation
       let success = true; // Example condition
       
       if(success) {
           resolve("Operation was successful!");
       } else {
           reject("Operation failed.");
       }
   });

3. Handling Promises:

- .then(): Used to handle a successful outcome.

- .catch(): Used to handle errors or rejections.

- .finally(): Executes code regardless of the promise's outcome.

   javascript
   promise.then(result => {
       console.log(result); // Operation was successful!
   }).catch(error => {
       console.log(error); // Operation failed.
   }).finally(() => {
       console.log("Operation complete.");
   });

Why Use Promises?

Promises simplify handling asynchronous operations, especially when dealing with sequences of asynchronous tasks. They enable chaining, which allows for cleaner code:

javascript
doSomething()
   .then(result => doSomethingElse(result))
   .then(newResult => doAnotherThing(newResult))
   .catch(error => console.log(error));