how to log data into a new file?-CodePudding

I'm a beginner to node.js, started to learn just a few days ago. i'm trying to log the listener's data into a new file by using fs.appendFile, but no matter how many times i try to change the code, it keeps giving me an ERR-INVALID-CALLBACK.

const Logger = require('./logger_demo')
const logger = new Logger
const fs = require('fs')
logger.on('message', data => console.log('Called Listener: ', data))
fs.appendFile('./log_demo.js', 'message', (err) => {
  if (err) throw err
  console.log('File has been appended!')
})

fs.appendFile(logger.log('Hello World!'))

I'm not sure what I'm doing wrong, any idea how to solve this?

CodePudding user response：

fs.appendFile(logger.log('Hello World!'))

this line is your problem you are calling fs.appendFile with wrong parameters

CodePudding user response：

I think the issue may be here:

const logger = new Logger

Should it be this?

const logger = new Logger()

Additionally, you need to give a file-path to fs.appendFile:

fs.appendFile("log.txt", logger.log('Hello World!'))

But I think you meant to do this:

logger.log('Hello World!')