export module for multiple functions

Question

I am new to node and I am trying learn the different ways you can use export module to make my code easier to read because they are in separate files. I have want to take my program response functions out of my callback.js file and move them into a separate file called progresponse.js but I am getting errors because it is not reading the emit method on the emitter.js file. The emitter.js and callback.js code works. But I am trying to get the emitter.js, wanttomodularize.js and progresponses.js code to work.

my progresponses.js and wanttomodularize.js code was my attempt at separating that code. This code gives the error that it doesn't recognize some emitter.js methods.

I apologize ahead of time if this is a lot and very specific to my learning but could someone show me how I can take the bolded text out of callback.js and put it into a separate file (progresponse.js)?

emitter.js

function Emitter(){
  this.events = {};
}

Emitter.prototype.on = function( type, listener){
  this.events[type] = this.events[type] || [];
  this.events[type].push(listener);
}

Emitter.prototype.emit = function(type){
  if(this.events[type]){
    this.events[type].forEach(function(listner){
      listner();
    });
   }
}

module.exports = Emitter;

callback.js (this code works with emitter.js)

var Emitter = require('./emitter.js'); 

const readline = require('readline');
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: 'Speak Chinese> '
});

var user = {
  "name" : "something",
  "response" : ""
};

var emtr = new Emitter();

function 你好(callback) {

  var data = {
      programResponse: '你好！'
  };

  console.log(data.programResponse);
  callback(data);
}

function 你在干什么(callback) {

  emtr.on('你在干什么', function(){
    console.log('我在喝咖啡。');
    console.log(user.name +'，你呢，你在干什么？');
  });

  callback();
}

function 你猜猜(callback) {

  emtr.on('你猜猜', function(){
    console.log('我不知道。'+ user.name +'，你在干什么？');
  });

  callback();
}

function 对(callback) {
  emtr.on('对', function(){
    console.log('真棒');
  });

  callback();
}

rl.question('What is your name? ', (answer) => {
  // TODO: Log the answer in a database
  user.name = answer;
  console.log(`Thank you for your valuable feedback: ${answer}`);
});

rl.prompt();

rl.on('line', (line) => {
  switch (line.trim()) {
    case '你好':你好(function(){}); 
      break;
    case '你在干什么':你在干什么(function(){emtr.emit('你在干什么')});
      break;
    case '你猜猜':你猜猜(function(){emtr.emit('你猜猜')});
      break;
    case '对':对(function(){emtr.emit('对')});   
      break;
    default:
      console.log(`Interesting, you said '${line.trim()}'?`);
      break;
  }
  rl.prompt();
}).on('close', () => {
  console.log('再见！');
  process.exit(0);
});

wanttomodularize.js

var Emitter = require('./emitter.js'); 
var callback = require('./progresponses.js');
const readline = require('readline');
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  prompt: 'Speak Chinese> '
});

var user = {
  "name" : "something",
  "response" : ""
};


rl.question('What is your name? ', (answer) => {
  // TODO: Log the answer in a database
  user.name = answer;
  console.log(`Thank you for your valuable feedback: ${answer}`);
});

rl.prompt();

rl.on('line', (line) => {
  switch (line.trim()) {
    case '你好':callback.你好(function(){}); 
      break;
    case '你在干什么':callback.你在干什么(function(){callback.emtr.emit('你在干什么')});
      break;
    case '你猜猜':callback.你猜猜(function(){callback.emtr.emit('你猜猜')});
      break;
    case '对':callback.对(function(){callback.emtr.emit('对')});   
      break;
    default:
      console.log(`Interesting, you said '${line.trim()}'?`);
      break;
  }
  rl.prompt();
}).on('close', () => {
  console.log('再见！');
  process.exit(0);
});

progresponses.js

var Emitter = require('./emitter.js'); 
var emtr = new Emitter();

module.exports = {
  你好: function 你好(callback) {

    var data = {
        programResponse: '你好！'
    };

    console.log(data.programResponse);
    callback(data);
  },
  你在干什么: function 你在干什么(callback) {

    emtr.on('你在干什么', function(){
      console.log('我在喝咖啡。');
      console.log(user.name +'，你呢，你在干什么？');
    });

    callback();
  },
  你猜猜: function 你猜猜(callback) {

    emtr.on('你猜猜', function(){
      console.log('我不知道。'+ user.name +'，你在干什么？');
    });

    callback();
  },
  对: function 对(callback) {

    emtr.on('对', function(){
      console.log('真棒');
    });

    callback();
  }
}

This is the error I get when running:

node wanttomodularize.js

Bretts-MacBook-Pro:clinput codesankofa$ node wanttomodularize.js
What is your name? DOM
Thank you for your valuable feedback: DOM
你在干什么
readline.js:1021
            throw err;
            ^

TypeError: Cannot read property 'emit' of undefined
    at /Users/codesankofa/CodingWorkspace/NodePractice/clinput/wanttomodularize.js:28:58
    at Object.你在干什么 (/Users/codesankofa/CodingWorkspace/NodePractice/clinput/progresponses.js:21:5)
    at Interface.rl.on (/Users/codesankofa/CodingWorkspace/NodePractice/clinput/wanttomodularize.js:28:27)
    at emitOne (events.js:116:13)
    at Interface.emit (events.js:211:7)
    at Interface._onLine (readline.js:282:10)
    at Interface._line (readline.js:631:8)
    at Interface._ttyWrite (readline.js:911:14)
    at ReadStream.onkeypress (readline.js:160:10)
    at emitTwo (events.js:126:13)

Steven Spungin · Accepted Answer

You are using emtr from callback, but you have not assigned it to the exported object. You need to include it before exporting.

//wanttomodularize.js

var callback = require('./progresponses.js');
//...
callback.emtr.emit

// progresponses.js

module.exports = {
  emtr, // <-----

  你好: function 你好(callback) {

    var data = {
        programResponse: '你好！'
    };

    console.log(data.programResponse);
    callback(data);
  },

export module for multiple functions

Answers (2)

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