nodeEvents2.js

var util = require('util'),
  eventEmitter = require('events').EventEmitter,
  fs = require('fs');

function inputChecker(name, file) {
  this.name = name;
  this.writeStream = fs.createWriteStream('./'+ file + ".txt",
      {
        'flags': 'a',
        'encoding': 'utf8',
        'mode': '0666' 
      });
}
// melds inputChecker with eventEmitter together
util.inherits(inputChecker, eventEmitter);

// function that check the input
inputChecker.prototype.check = function check(input) {
  var command = input.toString().trim().substr(0,3);
  if (command == 'wr:' ) {
    // if the command starts with 'wr:', then emit an event
    // 'write' and the callback function is transformation
    // of the input string without the first 3 chars (=== command)
    this.emit('write', input.substr(3, input.length));
  } else if (command == 'en:') {
    // if the command starts with 'en:' the program emits 'end' and the
    // .on listeners executes process.exit();
    this.emit('end');
  } else {
    // if none of above matches to the command, just emit the 'echo' event
    //
    this.emit('echo', input);
  }
};

// new object testing and event handling
var ic = new inputChecker('ACustomString','outputfile');

ic.on('write', function(data) {
  this.writeStream.write(data, 'utf8');
});


ic.on('echo', function(data) {
  console.log(this.name + " wrote " + data);
});

ic.on('end', function() {
  process.exit();
});

process.stdin.resume();
process.stdin.setEncoding('utf8');
process.stdin.on('data', function(input) {
 ic.check(input);
});