Use Cases of Node.js

HTTP server

const http = require('http');

console.log('Starting server...');
var config = {
    port: 80,
    contentType: 'application/json; charset=utf-8'
};
// JSON-API server on port 80

var server = http.createServer();
server.listen(config.port);
server.on('error', (err) => {
    if (err.code == 'EADDRINUSE') console.error('Port '+ config.port +' is already in use');
    else console.error(err.message);
});
server.on('request', (request, res) => {
    var remoteAddress = request.headers['x-forwarded-for'] || request.connection.remoteAddress; // Client address
    console.log(remoteAddress +' '+ request.method +' '+ request.url);
    
    var out = {};
    // Here you can change output according to `request.url`
    out.test = request.url;
    res.writeHead(200, {
        'Content-Type': config.contentType
    });
    res.end(JSON.stringify(out));
});
server.on('listening', () => {
    c.info('Server is available: http://localhost:'+ config.port);
});

Console with command prompt

const process = require('process');
const rl = require('readline').createInterface(process.stdin, process.stdout);

rl.pause();
console.log('Something long is happening here...');

var cliConfig = {
    promptPrefix: ' > '
}

/*
    Commands recognition
    BEGIN
*/
var commands = {
    eval: function(arg) { // Try typing in console: eval 2 * 10 ^ 3 + 2 ^ 4
        arg = arg.join(' ');
        try { console.log(eval(arg)); }
        catch (e) { console.log(e); }
    },
    exit: function(arg) {
        process.exit();
    }
};
rl.on('line', (str) => {
    rl.pause();
    var arg = str.trim().match(/([^"]+)|("(?:[^"\\]|\\.)+")/g); // Applying regular expression for removing all spaces except for what between double quotes: http://stackoverflow.com/a/14540319/2396907
    if (arg) {
        for (let n in arg) {
            arg[n] = arg[n].replace(/^\"|\"$/g, '');
        }
        var commandName = arg[0];
        var command = commands[commandName];
        if (command) {
            arg.shift();
            command(arg);
        }
        else console.log('Command "'+ commandName +'" doesn\'t exist');
    }
    rl.prompt();
});
/*
    END OF
    Commands recognition
*/

rl.setPrompt(cliConfig.promptPrefix);
rl.prompt();