JavaScript Async Example

app.js

function isSuccess(success) {
    return new Promise(function (resolve, reject) {
        if (success === true) {
            resolve('Success');
        } else {
            reject('Error');
        }
    });
}

console.log(0);

let promise1 = isSuccess(true);

promise1.then(function (success) {
  console.log(success);
}).catch(function (err) {
    console.log(err);
});

const promise2 = isSuccess(false);

promise2.then(function (success) {
    console.log(success);
}).catch(err => {
    console.log(err);
})

console.log(3);