Private variables with TypeScript + WeakMaps

README.md

This example needs (WeakMaps)[http://kangax.github.io/compat-table/es6/#WeakMap] which almost has full support on modern Chrome/Firefox.

For information about the implmentation, read: https://developer.mozilla.org/en-US/Add-ons/SDK/Guides/Contributor_s_Guide/Private_Properties

ES5-Number.js

var Number;
(function (Number_1) {
    var map = new WeakMap();
    var internal = function (object) {
        if (!map.has(object))
            map.set(object, {});
        return map.get(object);
    };
    var Number = (function () {
        function Number(x) {
            internal(this)._x = x;
        }
        Object.defineProperty(Number.prototype, "x", {
            get: function () {
                return internal(this)._x;
            },
            set: function (x) {
                 console.log('wtf');
                internal(this)._x = x;
            },
            enumerable: true,
            configurable: true
        });
        return Number;
    })();
    Number_1.Number = Number;
})(Number || (Number = {}));
var myNumber = new Number.Number(4);
console.log(myNumber); // {}
console.log("Direct access " + myNumber._x); // undefined
console.log("Getter access " + myNumber.x); // 4
myNumber.x = 54;
console.log(myNumber.x); // 54

ES6-Number.js

var Number;
(function (Number_1) {
    let map = new WeakMap();
    let internal = function (object) {
        if (!map.has(object))
            map.set(object, {});
        return map.get(object);
    };
    class Number {
        constructor(x) {
            internal(this)._x = x;
        }
        get x() {
            return internal(this)._x;
        }
        set x(x) {
            internal(this)._x = x;
        }
    }
    Number_1.Number = Number;
})(Number || (Number = {}));
var myNumber = new Number.Number(4);
console.log(myNumber); // {}
console.log(`Direct access ${myNumber._x}`); // undefined
console.log(`Getter access ${myNumber.x}`); // 4
myNumber.x = 54;
console.log(myNumber.x); // 54

Number.ts

module Number {
  let map = new WeakMap();

  let internal = function (object) {
    if (!map.has(object))
      map.set(object, {});
      return map.get(object);
  }
  export class Number {

    constructor(x: number) {
      internal(this)._x = x;
    }

    get x(): number {
      return internal(this)._x;
    }

    set x(x: number) {
      internal(this)._x = x;
    }
  }
}

var myNumber = new Number.Number(4);
console.log(myNumber); // {}
console.log(`Direct access ${myNumber._x}`); // undefined
console.log(`Getter access ${myNumber.x}`);  // 4

myNumber.x = 54;
console.log(myNumber.x) // 54