Javascript topic on Promises

1. PROMISES IN JAVASCRIPT

2. Introduction
• A Promise in JavaScript represents a value that may be
available now, later, or never.
• It is used to handle asynchronous operations efficiently.

3. Why Use Promises?
• Avoid callback hell (pyramid of doom)
• Better error handling
• Easier to read and maintain

4. States of a Promise
1. Pending – Initial state, the operation is not complete.
2. Fulfilled – Operation completed successfully.
3. Rejected – Operation failed.

5. Creating a Promise
let myPromise = new Promise((resolve,
reject) => {
let success = true;
if (success) {
resolve("Operation Successful");
} else {
reject("Operation Failed");
}
});

6. Handling a Promise
• Using .then() and .catch()
myPromise
.then(result =>
console.log(result)) // Success handling
.catch(error =>
console.log(error)); // Error handling
• Using async/await (Modern approach)
async function handlePromise() {
try {
let result = await myPromise;

7. Chaining Promises
fetch('https://api.example.com/data')
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.log(error));

8. Promise Methods
Promise.all()
• Waits for all promises to resolve or rejects if any fail.
Promise.all([promise1,
promise2]).then(results =>
console.log(results));
Promise.race()
• Returns the result of the first resolved or rejected promise.
Promise.race([promise1,
promise2]).then(result =>

9. Conclusion
• Promises make asynchronous programming more
manageable.
• Use async/await for better readability.
• Know Promise methods for handling multiple async tasks.

10. End of Presentation