module.exports function undefined when passing in a variable

Question

In my Node.js app, I'm passing in variables to functions by using require like so:

console.log(require('../controllers/controller')(variable)); // undefined

However, when I don't pass in the variable, it logs as a function, like so:

console.log(require('../controllers/controller')); // [Function]

My controllers are defined like this:

var Controller = function (variable) {
  this.variable = variable;
};

Controller.prototype.method = function (someInput, callback) {
  // can access this.variable;
};

module.exports = Controller;

I also get this error:

TypeError: Object function (variable) {
  this.variable = variable;
} has no method 'method'

Any idea as to where I'm going wrong here? I'm stuck at this step and not sure how to debug further.

Josh Smith · Accepted Answer · 2012-01-11 20:58:15Z

4

require('../controllers/controller') is a function. When you use it without new keyword it does not return anything. But when you use new function() it acts like a constuctor of the object. So what you want to do is to use new keyword if you need an object to be returned with its prototype methods.

var Controller = require('../controllers/controller'),
controller = new Controller(variable);

edited Jan 11, 2012 at 20:58

Josh Smith

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answered Jan 11, 2012 at 20:54

dfsq

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1 Comment

Josh Smith Over a year ago

Wow, that was a dumb mistake. Editing your answer to show exactly what I should have done for others who make the same stupid mistake.

davibq · Accepted Answer · 2014-03-12 18:31:54Z

1

this is an old thread, but I had this issue and the accepted answer didn't help me.

To create a module with a parameter, I use this code:

module.exports = function(pName) {
  return {
    test1: function() {
       console.log('In test 1 '+pName);
    },
    test2: function() {
       console.log('In test 2 '+pName);
    }
  };
};

And to call the module's functions:

var testModule = require('testModule')('David');
testModule.test1();
testModule.test2();

answered Mar 12, 2014 at 18:31

davibq

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