Private members in Javascript. Can they be non-static?

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

Answer 2

Use this.

var Person = (function() {
  var PersonConstructor = function(n) {
    this.name = n;
  };

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

  return PersonConstructor;    
})();

Unfortunately, this won't preserve the private state.

Answer 3

It's just a scope issue.

var Person = (function(){

    var PersonConstructor = function(n){ 
        // *************************************************************** 
        // PRIVATE VARIABLES AND FUNCTIONS 
        // ONLY PRIVELEGED METHODS MAY VIEW/EDIT/INVOKE 
        // *************************************************************** 

        var myName=n?n:"John Doe";

        // *************************************************************** 
        // PRIVILEGED METHODS 
        // MAY BE INVOKED PUBLICLY AND MAY ACCESS PRIVATE ITEMS 
        // MAY NOT BE CHANGED; MAY BE REPLACED WITH PUBLIC FLAVORS 
        // *************************************************************** 
        this.toString=this.getName=function(){ return myName } 
    } 
    return PersonConstructor;
})();

var person1 = new Person("foo");
var person2 = new Person("bar");

alert(person1.getName());
alert(person1.toString());
alert(person1.myName);

// alerts "foo", "foo", undefined

EDIT - Here is my original solution.

var Person = function(n){ 
    // *************************************************************** 
    // PRIVATE VARIABLES AND FUNCTIONS 
    // ONLY PRIVELEGED METHODS MAY VIEW/EDIT/INVOKE 
    // *************************************************************** 

    var myName=n?n:"John Doe";

    // *************************************************************** 
    // PRIVILEGED METHODS 
    // MAY BE INVOKED PUBLICLY AND MAY ACCESS PRIVATE ITEMS 
    // MAY NOT BE CHANGED; MAY BE REPLACED WITH PUBLIC FLAVORS 
    // *************************************************************** 
    this.toString=this.getName=function(){ return myName } 

} 

var person1 = new Person("foo");
var person2 = new Person("bar");

alert(person1.getName());
alert(person1.toString());
alert(person1.myName);

// alerts "foo", "foo", undefined