What is the use of Promises in JavaScript ?

Promises in JavaScript are a way to handle asynchronous operations. They have three states: pending, fulfilled, and rejected. You create a promise using the Promise constructor, and it resolves with a value or rejects with an error. Promises are consumed .then() for success and .catch() for errors. They support chaining for sequential operations and can be simplified with async/await a more synchronous-like syntax. Promises improve code readability and help avoid callback hell.

Syntax:

let promise = new Promise(function(resolve, reject){
     //do something
});

Example: This example shows how to create a basic promise object.

Javascript

let promise = new Promise(function (resolve, reject) {
    const x = "geeksforgeeks";
    const y = "geeksforgeeks"
    if (x === y) {
        resolve();
    } else {
        reject();
    }
});

promise.
    then(function () {
        console.log('Success, You are a GEEK');
    }).
    catch(function () {
        console.log('Some error has occurred');
    });

Output

Success, You are a GEEK