test-privates.html

<script>

//This is just for the purposes of this test file; in a real application you should use an AMD loader
//such as this: https://github.com/cujojs/curl
var simpleoo;
function define(dependencies, definition) {
    simpleoo = definition();
}

</script>
<script src="simpleoo.js"></script>
<script>

var log = console.log;
var extend = simpleoo.extend;
var mixin = simpleoo.mixin;
var deepCopy = simpleoo.deepCopy;


//http://tc39wiki.calculist.org/es6/symbols/

(function() {
"use strict";

var secret = 'secret code';

var isOlderBrowser = false;

function Symbol(internalName, isPrivate) {
    this.internalName = internalName;
}
Symbol.prototype.toString = function() {
    var ret = secret + this.internalName;
    
    //MAY NOT WANT TO AUTOMATICALLY SUPPORT OLDER BROWSERS...FOR THIS EXAMPLE, WE DON'T WANT THEM TO BE ABLE TO MODIFY THEIR
    //SCORE...SO IF THERE'S A WAY TO MAKE IT FOOLPROOF ON ES5 BUT NOT EARLIER, THEN THERE SHOULD BE AN OPTION TO *NOT*'
    //SUPPORT IT ON OLDER BROWSERS
    
    //start with _private so that older browsers that don't support Object.defineProperty to create non-enumerable properties
    //will still see a clear indication that the property is private
    if (!Object.defineProperty) return '_private_' + ret;
    return ret;
}

function PrivateProperty(obj, name) {
    this.name = name;
    
    //We might not need this, but we should have some way of checking to see if the property was actually added to the
    //object using defineProperty before allowing it to be used
    this.initialized = false;
}
PrivateProperty.prototype = makePrototype(PrivateProperty, extend(Symbol.prototype));

var score = new Symbol('score', true);

function definePrivateProperty(obj, propName, defaultVal) {
    if (defaultVal == undefined) defaultVal = null;
    //the property will not be enumerable or configurable, since those
    //default to false
    Object.defineProperty(obj, secret + propName, {value:defaultVal, writable:true});
}

window.Player = function Player() {
    definePrivateProperty(this, 'score');
    
    this[score] = 0;    
    increaseScore(this, 1);
}

Player.prototype.getScore = function() {
    return this[score];
}

function increaseScore(player, n) {
    player[score] += n;
}

})();

var log = console.log;
var player = new Player();
log(player.getScore());
log(player.score);

log(player);


</script>