====== JavaScript: Promises ======

<code javascript>
const fs = require('fs');

function readFilePromised(filename) {
    return new Promise(function (resolve, reject) {
        fs.readFile(filename, (err, data) => {
            if (err) {
                reject(err);
            }
            resolve(data.toString());
        });
    });
}

function writeFilePromised(filename, data) {
    return new Promise(function (resolve, reject) {
        fs.writeFile(filename, data, (err, data) => {
            if (err) {
                reject(err);
            }
            resolve();
        });
    });
}

const promise = readFilePromised('main.js');

promise.then((res) => {
    console.log(res);
}).then((err) => {
    console.log(err);
});

function react(request, response) {
    const pagename = 'test';
    const promise = readFilePromised(pagename + '.txt');
    promise.then((res) => {
        response.end(res);
        console.log('Delivered page: ' + pagename);
    }).then((err) => {
        response.status = 404;
        response.end();
        console.log(err);
    });
}
</code>