JavaScript Promises

What are Promises?

Promises are used to handle asynchronous operations in JavaScript. They represent a value that may be available now, in the future, or never.

Creating a Promise

You can create a promise using the Promise constructor. It takes a function with two arguments: resolve and reject.

Example: Creating a Promise

const myPromise = new Promise((resolve, reject) => {
    setTimeout(() => {
        resolve("Success!");
    }, 1000);
});
        

Handling Promises

Use .then() to handle resolved promises and .catch() to handle rejected promises.

Example: Handling a Promise

myPromise
    .then(result => {
        console.log(result); // "Success!"
    })
    .catch(error => {
        console.error(error);
    });
        

Chaining Promises

You can chain multiple promises using .then(). Each .then() returns a new promise.

Example: Chaining Promises

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

Async/Await

Async/await is a modern way to handle promises. It makes asynchronous code look synchronous.

Example: Async/Await

async function fetchData() {
    try {
        const response = await fetch('https://api.example.com/data');
        const data = await response.json();
        console.log(data);
    } catch (error) {
        console.error(error);
    }
}
        

Call for Live Sessions

Want to learn more? Call us at 078 777 0000 to arrange a live session with our experts!