Question

This may be a general javascript or jQuery question- I’m using backbone.js and I’d like to have a private method in one class that can be used by subclasses. Is this possible?

var fooView = Backbone.View.extend({
  initialize: function () {
    this._privateFunc();
  },
  _privateFunc: function () {
  ...
  }
});

var subFooView = fooView.extend({
  initialize: function () {
    this.coolFunc();
    this._privateFunc();
  },
  coolFunc: function () {
  ...
  }
});

But then _privateFunc is not exposed to the outside world. I’m pretty new to encapsulation in javascript so forgive me if there’s an obvious answer. 😀

Answer 1

What you’re looking for is more accurately called protected rather than private accessibility. There’s no way to directly implement this in JavaScript.

Your best bet is probably just to expose _privateFunc and use the convention that methods with underscores are only intended to be used by subclasses.

You could also implement __noSuchMethod__ in the parent and then check that the method is being called by a subclass and execute the protected method. However, this is a Mozilla extension.