Getting undefined when trying to call a method using a factory in JavaScript

Question

Trying to use composition over inheritance with factory functions in Javscript and I am getting function is not defined with the following code:

(dogIsCreated is not defined)

var dog = function dog(state) {
  return {
    create: function create() {
      console.log('Create the dog');
      dogIsCreated();
    },
    dogIsCreated: function dogIsCreated() {
      console.log('Ready');
    }
  }
}

var ted = dog().create();

Be amazing if someone could point me in the right direction? Am I using completely the wrong syntax.

Thanks :)

There is no function with name dogIsCreated (at least in the scope you are trying to call it from). dogIsCreated is a property on the object. Maybe you meant this.dogIsCreated() ? — Felix Kling
– Felix Kling, Commented Jan 14, 2016 at 16:06

Lloyd Banks · Accepted Answer · 2016-01-14 16:08:26Z

1

You need to define the scope the create() method is apart of using the this keyword.

var dog = function dog(state) {
  return {
    create: function create() {
      console.log('Create the dog');
      this.dogIsCreated();
    },
    dogIsCreated: function dogIsCreated() {
      console.log('Ready');
    }
  }
}

answered Jan 14, 2016 at 16:08

Lloyd Banks

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1 Comment

Felix Kling Over a year ago

The explanation reads a bit strange. It sounds like we have to change the visibility of create (which we don't).

saikumar · Accepted Answer · 2016-01-14 16:13:21Z

1

This (dogIsCreated)is not a global function. dogIsCreated function created with dog Object. this is object method , so you are calling this method inside another (same)object method, so we can call that method using 'this'–

var dog = function dog(state) {
  return {
    create: function create() {
      console.log('Create the dog');
      this.dogIsCreated();
    },
    dogIsCreated: function dogIsCreated() {
      console.log('Ready');
    }
  }
}

var ted = dog().create();

edited Jan 14, 2016 at 16:13

answered Jan 14, 2016 at 16:08

saikumar

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3 Comments

Felix Kling Over a year ago

Code without explanation is rarely helpful. No one likes to play the "spot the difference" game.

saikumar Over a year ago

This (dogIsCreated)is not a global function. dogIsCreated function created with dog Object. this is object method

Felix Kling Over a year ago

Basically yes. You can edit your answer to provide more information.

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