Question

I have this code here:

var Person = (function() {
    var name;

    var PersonConstructor = function(n) {
        name = n;
    };

    PersonConstructor.prototype.getName = function() {
        return name;
    };

    return PersonConstructor;

})();

var people = [];
var person1 = new Person("Foo");
var person2 = new Person("Bar");
alert(person1.getName()); // I want it to be Foo
people.push(person1);
people.push(person2);

I got the idea of emulating classes from here.. But of course, I neglected the fact that the private variable var name; is also a static variable. Since this is tripping my current efforts I would like to know if there is a way to keep the private behaviour in this example but avoid the static one?

Answer 1

There is no “private” when working with prototypes.

It should be noted there is no value in private state, avoid it like the plague. Closures are ugly and expensive.

var o = {
    name: value
}

However if you insist on being delusional and want private state badly then

You can store state in a closure

function nameHolder(name) {
    return {
        get name() {
            return name
        },
        set name(n) {
            name = n
        }
    }
}

Note this is highly inefficient and has little benefit.

Alternatively you can store state in a weakmap

function privates() {
    var map = new WeakMap()

    return function (key) {
        var v = map.get(key)
        if (!v) {
            v = {}
            map.set(key, v)
        }
        return v
    }
}

var NameHolder = (function () {
    var state = privates()

    return {
        constructor: function (name) {
            state(this).name = name
        },
        getName: function () {
            return state(this).name
        }
    }
}())

WeakMap browser support is non-existant so emulate it using pd.Name