eventcallback.js

var EventEmitter = require('events').EventEmitter;
var emitter = new EventEmitter();
var fs = require('fs');
// Event to read file - generic function.
emitter.on('start_read',function(file_name) {
  console.log("Started Reading file....\n\n");
  fs.readFile(file_name, 'utf8', function (err,data) {
    if (err) {
      console.log("Error happens.");
    } else {
      console.log("File data", data);
    }
  });
});
// Let's read some file.
emitter.emit('start_read','env.json');
emitter.emit('start_read','envConfig.js');