Is this the correct way to do private functions in Javascript / node.js?

Question

A class I'm writing in node.js is as below:

module.exports = exports = function(){ return new ClassA() };

function ClassA(){
    this.myvariable = 0;
}

I have a function that I want to be private. To my understanding if the function is declared outside of the constructor, it will essentially be a static function which wouldn't be able to reference this.myvariable.

Is the correct way of dealing with this to declare the function within the constructor like this:

//within constructor
this.myFunction = function myFunction(){
    console.log(this.myvariable)
}

Or is there a better way of doing it that doesn't leave me with a potentially huge constructor?

EDIT: It looks like I've misunderstood something here because the above code doesn't even work...

Answer 1

Simplest way to have a private function is to just declare a function outside of the class. The prototype functions can still reference it perfectly fine, and pass their this scope with .call()

function privateFunction() {
  console.log(this.variable)
}

var MyClass = function () {
  this.variable = 1;
}

MyClass.prototype.publicMethod = function() {
  privateFunction.call(this);
}

var x = new MyClass();
x.publicMethod()