JavaScriptEasy

What are Promises and how do they work?

By FrontendPro Editorial Team Updated 8/8/2026

#JavaScript

Answer

Promises in JavaScript are objects that represent the eventual completion (or failure) of an asynchronous operation and its resulting value. They have three states: pending, fulfilled, and rejected. You can handle the results of a promise using the .then() method for success and the .catch() method for errors.

let promise = new Promise((resolve, reject) => {
  // asynchronous operation
  const success = true;
  if (success) {
    resolve("Success!");
  } else {
    reject("Error!");
  }
});

promise
  .then((result) => {
    console.log(result); // 'Success!' (this will print)
  })
  .catch((error) => {
    console.error(error); // 'Error!'
  });