Node.js Async Patterns

fs.readFile('file.txt', (err, data) => { # callback pattern
    if (err) throw err;
    console.log(data);
});

const promise = new Promise((resolve, reject) => {
    if (success) resolve(data);
    else reject(error);
});
promise
    .then(data => console.log(data))
    .catch(err => console.error(err));

async function readFile() { # async function
    try {
        const data = await fs.promises.readFile('file.txt');
        console.log(data);
    } catch (err) {
        console.error(err);
    }
}

const results = await Promise.all([ # parallel execution
    fetchUser(),
    fetchPosts(),
    fetchComments()
]);

const result = await Promise.race([ # first to complete
    fetchFromAPI1(),
    fetchFromAPI2()
]);

process.on('unhandledRejection', (err) => { # catch unhandled rejections
    console.error(err);
    process.exit(1);
});