Javascript constructor to access own private method?

Question

I have a method in my class that I do not want to be public. I'm wondering if it's possible to access the method from the constructor?

For example:

(function () {
    var Config = function() {
        this.data = this.getOptions();
        var options = document.querySelector('.options');
        options.addEventListener('click', this.toggleOption, false);
    };

    Config.prototype = function() {
        var getOptions = function() {
            // public method
        },

        toggleOption = function() {
            // private method
        };

        return {
            getOptions: getOptions
        };
    }();

    var config = new Config();

})();

My apologies if this has been asked before, but is this possible?

Sorry there was a mistake in my code, the function assigned to the prototype is supposed to be self-invoking. I'm trying out the "Revealing Prototype Pattern" --it's still new to me. — j_quelly
– j_quelly, Commented Apr 11, 2016 at 2:08
I see now. You can declare toggleOption in the outer scope, inside the IIFE, it will still be "private". But this "private" and "public" concept doesn't transfer to JS too well, not in the classical OOP sense. — elclanrs
– elclanrs, Commented Apr 11, 2016 at 2:10
There's no need to wrap the prototype object creation in an IIFE when the whole class already is in one. — Bergi
– Bergi, Commented Apr 11, 2016 at 3:08

user1031721 · Accepted Answer · 2016-04-11 02:13:34Z

1

Yes, it is possible :D

Demo: https://jsbin.com/xehiyerasu/

(function () {
  var Config = (function () {
    function toggleOption () {
      console.log('works')
    }

    var Config = function() {
        this.data = this.getOptions();
        var options = document.querySelector('.options');
        options.addEventListener('click', toggleOption.bind(this), false);
    };

    Config.prototype = (function() {
        var getOptions = function() {
            // public method
        };
        return {
            getOptions: getOptions
        };
    })();

    return Config;
  })();

  var config = new Config();

  console.log('Is toggleOption private? ', !config.toggleOption)

})();

answered Apr 11, 2016 at 2:13

user1031721

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1 Comment

user1031721 Over a year ago

Note: most important part is .bind(this) which makes the object instance available to the toggleOption function.

Jeremy J Starcher · Accepted Answer · 2016-04-11 02:06:55Z

0

It depends on WHY you'd like to expose this.

If, for instance, you want to expose that variable for unit testing purposes, you could do something like:

if (window.someUnitTestingGlobal) {
  var gprivate = {
    toggleOption: toggleOption
  };
}


return {
    getOptions: getOptions,
    gprivate: gprivate
};

answered Apr 11, 2016 at 2:06

Jeremy J Starcher

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