Answers for "callback in node js"

using multiparty with node js express

var express = require('express');
var multiparty = require('connect-multiparty'),
    multipartyMiddleware = multiparty({ uploadDir: './imagesPath' });

var router = express.Router();

router.post('/', multipartyMiddleware, function(req, res) {
  console.log(req.body, req.files);
  var file = req.files.file;
  console.log(file.name);
  console.log(file.type);
  res.status(200).send('OK');
});

module.exports = router;

node js callback

function processData (callback) {
  fetchData(function (err, data) {
    if (err) {
      console.log("An error has occurred. Abort everything!");
      return callback(err);
    }
    data += 1;
    callback(null, data);
  });
}

processData(function (err, data) {
  if (err) {
      console.err(err);
  } else {
    console.log("Data: " + data);
  }
});

writefile in node js

// append_file.js

const fs = require('fs');

// add a line to a lyric file, using appendFile
fs.appendFile('empirestate.txt', '\nRight there up on Broadway', (err) => {
    if (err) throw err;
    console.log('The lyrics were updated!');
});

writefile in node js

fs.writeFile('2pac.txt', 'Some other lyric', 'ascii', callback);

callback in js

function greeting(name) {
  alert('Hello ' + name);
}

function processUserInput(callback , {
  var name = prompt('Please enter your name.');
  callback(name);
}}

processUserInput(greeting);