node.js要求不全局加载对象

Question

I have two files in helpers folder, one is EventHelper.js and UserEvent.js ,

helpers/EventHelper.js

function EventHelper() {
  this.onEventCreated = function(err, e) {...}
  this.isExisting = function(id) {...}
}
module.exports = new EventHelper();

helpers/UserEvent.js

var EventHelper1 = require('./EventHelper')
var EventHelper2 = require('./EventHelper.js')

function UserEvent() {
  this.fireEvent = function(req, res) {
    var EventHelper3 = require('./EventHelper');
    ...
    EventHelper1.onEventCreated(err, e);
    EventHelper2.onEventCreated(err, e);
    EventHepler3.onEventCreated(err, e);
  }
};
module.exports = new UserEvent();

controllers/EventController.js

 var EventHelper = require('../helpers/EventHelper')
    var UserEvent = require('../helpers/UserEvent');

    var EventController = {
      fireEvent: function(req, res) {
        if(EventHelper.isExisting(req.params.id)) UserEvent.fireEvent(req, res)
        ...
      }
    }

EventHelper1 and EventHelper2 in UserEvent.js are always empty(having {} ), where as EventHelper3 is being initialised properly and able to refer object's methods properly. I have referred this EventHelper.js in different controllers folder( EventController.js ) globally and it was getting populated properly. I am not sure if I am missing something here

Answer 1

You're missing some semicolons:

function EventHelper() {
   this.onEventCreated = function(err, e) {...}
   this.isExisting = function(id) {...}
}**;**
module.exports = new EventHelper();

For instance after adding this one, I got the EventHelper within your Controller, which I haven't gotten before.

Furthermore (I guess it's just and typo here and not in your actual code, since then you couldn't get an instance for it), it's:

EventHelper3.onEventCreated(err,e);

and not `

EventHepler3.onEventCreated(err,e);

So to sum up, the following is now working for me:

// EventHelper.js
function EventHelper() {
   this.onEventCreated = function(err, e) {
      console.log('testCreate');
   };
   this.isExisting = function(id) {
      console.log('testExists' + id);
      return true;
   };
};  
module.exports = new EventHelper();

// UserEvent.js
var EventHelper1 = require('./EventHelper.js');
var EventHelper2 = require('./EventHelper.js');


function UserEvent() {
   this.fireEvent = function(req, res) {
      console.log(req + res);
      var EventHelper3 = require('./EventHelper');
      EventHelper1.onEventCreated(req, res);
      EventHelper2.onEventCreated(req, res);
      EventHelper3.onEventCreated(req, res);
   };
};
module.exports = new UserEvent();

// EventController.js
var EventHelper = require('../helpers/EventHelper.js');
var UserEvent = require('../helpers/UserEvent.js');

var EventController = {
   fireEvent: function(req, res) {
      if(EventHelper.isExisting(1)) UserEvent.fireEvent(req, res);
   };
 }

 EventController.fireEvent("1","2");

Withe the following output:

testExists1
12
testCreate
testCreate
testCreate

I hope that I could help you!