Promises in javascript

A Promise is an object that represents the future result of an asynchronous operation.

Example: API call, file reading, database query.

Promise  states -

1. Pending → still waiting
2. Fulfilled → completed successfully
3. Rejected → failed

Example:

const promise = new Promise((resolve, reject) => {
    
    let success = true;

    if(success){
        resolve("Task completed");
    } else {
        reject("Task failed");
    }
});

Here:

• resolve() → marks promise as fulfilled
• reject() → marks promise as rejected 
  

  To handle the result:

  promise
    .then(result => {
        console.log(result);
    })
    .catch(error => {
        console.log(error);
    });
  

  • .then() → runs if success
  • .catch() → runs if error