Promise in JavaScript...

In JavaScript, a Promise is an object representing the eventual completion or failure of an asynchronous operation.

Promise have 3 states:

1.Pending - Initial state, (waiting for response)
2.Fulfill- Operation completed successfully (resolve() was called)
3.Rejected - Operation failed (reject() was called)

Syntax for promise:

const promise = new Promise((resolve, reject) => { if (success) { resolve(result); } else { reject(error); } }); 

• resolve: Call this when the task is successful
• reject: Call this when the task fails

Example:

<script> function login() { return new Promise((resolve, reject) => { let password = true; if (password) { resolve(); } else { reject(); } }) } login() .then(() => console.log("successfully login...")) .catch(() => console.log("invalid password...")) </script> 

Output: