How Do I Call A Public Function From Within A Private Function In The JavaScript Module Pattern

How do I call a public function from within a private function in the JavaScript Module Pattern? For example, in the following code, var myModule = (function() { var private1 =

Solution 1:

You can use this to get the object your privileged method greet was called on.

Then, you can pass that value to your private method _sayHello, e.g. using call, apply, or as an argument:

var snowman4 = (function() {
    var _sayHello = function() {
        console.log("Hello, my name is " + this.name);
    };
    return {
        name: "Olaf",
        greet: function() {
            _sayHello.call(this);
        }
    };
})();

Now you can do

var snowman = Object.create(snowman4);
snowman.greet(); // "Hello, my name is Olaf"
snowman.name = "Frosty";
snowman.greet(); // "Hello, my name is Frosty"

And also

snowman4.greet(); // "Hello, my name is Olaf"
snowman4.name = "Frosty";
snowman4.greet(); // "Hello, my name is Frosty"

Solution 2:

With module pattern, you hide all the innates of an object in local variables/functions, and usually employ those in your public functions. Each time a new object is created with a module pattern, a new set of exposed functions - with their own scoped state - is created as well.

With prototype pattern, you have the same set of methods available for all objects of some type. What changes for these methods is this object - in other words, that's their state. But this is never hidden.

Needless to say, it's tough to mix those. One possible way is extracting the methods used by privates into a prototype of the module's resulting object with Object.create. For example:

var guardian = function() {
    var proto = {
        greet: function () {
            console.log('I am ' + this.name());
        },
        name: function() {
            return 'Groot';
        }
    };
    var public = Object.create(proto);
    public.argue = function() {
        privateGreeting();
    };

    var privateGreeting = public.greet.bind(public);
    return public;
};

var guardian1 = guardian();
guardian1.argue(); // I am Groot
var guardian2 = guardian();
guardian2.name = function() {
  return 'Rocket';
};
guardian2.argue(); // I am Rocket
var guardian3 = guardian();
guardian3.__proto__.name = function() {
  return 'Star-Lord';
};
guardian3.argue(); // I am Star-Lord