Error in Node.js callback must be a function?

Question

JavaScript

When calling this code in Node.js, an error occurs saying
TypeError [ERR_INVALID_CALLBACK] : Callback must be a function
, etc.
I don't understand what's the matter.

var fs  = require('fs');
const format = require('node.date-time');

function logTime() {
  return new Date().format('y-M-d H:M:S')+" ";
}

fs.appendFile('readme.log', logTime() + 'myText' + '\n');

Answer 1

The third parameter of the fs.appendFile function is to specify the function that will be called when the given function is executed. You can put an empty anonymous function there: function(){}