is there a way in JavaScript to inherit private members from a base class to a sub class?

I want to achieve something like this:

function BaseClass() {
  var privateProperty = "private";

  this.publicProperty = "public";
}

SubClass.prototype = new BaseClass();
SubClass.prototype.constructor = SubClass;

function SubClass() {
  alert( this.publicProperty );   // This works perfectly well

  alert( this.privateProperty );  // This doesn't work, because the property is not inherited
}

How can I achieve a class-like simulation, like in other oop-languages (eg. C++) where I can inherit private (protected) pr开发者_StackOverflow中文版operties?

Thank you, David Schreiber

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Using Douglas Crockfords power constructor pattern (link is to a video), you can achieve protected variables like this:

function baseclass(secret) {
    secret = secret || {};
    secret.privateProperty = "private";
    return {
        publicProperty: "public"
    };
}

function subclass() {
    var secret = {}, self = baseclass(secret);
    alert(self.publicProperty);
    alert(secret.privateProperty);
    return self;
}

Note: With the power constructor pattern, you don't use new. Instead, just say var new_object = subclass();.

---

Mark your private variables with some kind of markup like a leading underscore _ This way you know it's a private variable (although technically it isn't)

this._privateProperty = "private";
alert( this._privateProperty )

---

This isn't possible. And that isn't really a private property - it's simply a regular variable that's only available in the scope in which it was defined.

---

That can't be done, but you could delete the property from the class prototype so that it is not inherited:

SubClass.prototype.privateProperty  = undefined;

That way it won't be inherited, but you need to do that for every "private" property in your base class.

---

Just for reference if someone finds that today (October 2019) We can implement private properties in javascript using WeakMap()

const _privateProperty = new WeakMap();

class BaseClass {
    constructor(){
        this.publicProperty = 'public';
       _privateProperty.set(this, 'private');
    }
}

module.exports = BaseClass;

Inherits the BaseClass

const BaseClass = require('./BaseClass')

class ChildClass extends BaseClass{
   constructor(){
      super()
   }
}

This way your child class will inherit all the public properties from the BaseClass but the private ones.

Now, I am not sure whether one should take this approach but you can read the private properties from your parent class through your child class this way:

const _privateProperty = new WeakMap();

class BaseClass {
    constructor(){
        this.publicProperty = 'public';
       _privateProperty.set(this, 'private');
    }
    //Public method
    readProperties(){
      const property.private = _privateProperty.get(this);
      return property;
   }
}

module.exports = BaseClass;

Child Class

const BaseClass = require('./BaseClass')

class ChildClass extends BaseClass{
   constructor(){
      super()
   }
   //Public Method
   showProperties(){
      super.readProperties().private
   }
}

const properties = new ChildClass()
properties.showProperties()