using another javascript class within a different class

Question

In Swift I can instantiate one class within another as a property and call its methods using something like:

newClass.anotherClass.methodInTheOtherClass();

I am unable to do that in JavaScript. The following code produces an error in this line:

var cowCommunication = new CowCommunication();

What is the proper way to achieve this goal, and make the following script work?

<html >
  <script type = "text/javascript" >
  let CowCommunication = {
    sayMoo: function() {
      alert("hey");
    }
  };
let farmTools = {
  var cowCommunication = new CowCommunication();
};
farmTools.cowCommunication.sayMoo();

</script>
</html >

This is a real example of code I am actually trying to make work.

you can't use the var keyword inside of an object initializer in javascript, that's your main problem. look up the correct way to instantiate objects in javascript. — Mike Corcoran
– Mike Corcoran, Commented Feb 10, 2017 at 20:05

Abdennour TOUMI · Accepted Answer · 2017-02-10 20:12:40Z

4

let farmTools = {
  cowCommunication : new CowCommunication(),
};

Not

let farmTools = {
  var cowCommunication = new CowCommunication();
};

Also :

class CowCommunication  {

    sayMoo() {
      alert("hey");
    }
}

Not :

let CowCommunication = {
    sayMoo: function() {
      alert("hey");
    }
  }

edited Feb 10, 2017 at 20:12

answered Feb 10, 2017 at 20:05

Abdennour TOUMI

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4 Comments

Mark Purpelio Over a year ago

Thank you @Abdenour! I tried that and have received test.html:10 Uncaught TypeError: CowCommunication is not a constructor

Abdennour TOUMI Over a year ago

is it ok now ? @MarkPurpelio

Mark Purpelio Over a year ago

brilliant, Abdennour - yes! One final aspect: right now we have "farmTools.cowCommunication.sayMoo();" working. What if we wanted ONE MORE level, such as "farmTools.cowCommunication.newLevel.sayMoo();" ?

Abdennour TOUMI Over a year ago

class NewLevel { sayMoo(){} } ; class CowCommunication { constructor() {this.newLevel= new NewLevel();}}

thesublimeobject · Accepted Answer · 2017-02-10 20:15:49Z

0

You can also use composition instead of Classes.

let cowCommunication = {
    sayMoo: function() {
      console.log('hey')
    }
};

const farmTools = function() {
  return Object.assign({}, cowCommunication)
}

let instance = farmTools()

instance.sayMoo()

answered Feb 10, 2017 at 20:15

thesublimeobject

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2 Comments

Mark Purpelio Over a year ago

thank you! but you end up with "instance.sayMoo()" i need "farmTools.cowCommunication.sayMoo();" i need to the dots, the second class, and the method from the second class, so to speak

thesublimeobject Over a year ago

The method is actually from the second object, it's just not notated that way; it's just inherited from the first object by way of prototypes, which is sort of the Class system of JS.

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