Discussion on: Beginner's guide to creating a Node.js server

mood=Excited
fs.js:144
  throw new ERR_INVALID_CALLBACK(cb);
  ^
TypeError [ERR_INVALID_CALLBACK]: Callback must be a function. Received undefined
    at maybeCallback (fs.js:144:9)
    at Object.writeFile (fs.js:1325:14)
    at IncomingMessage.<anonymous> (E:\Users\Christopher\Documents\GitHub\All_The_Feels\routes.js:30:10)
    at IncomingMessage.emit (events.js:327:22)
    at endReadableNT (_stream_readable.js:1221:12)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) {
  code: 'ERR_INVALID_CALLBACK'
}

fs.writeFile("user_mood.txt", mood, function (err) {
    if (err) {
        return console.log(err);
    }
    console.log("File saved successfully!");
});