use.js

require("es6-shim");

var lib = (function () {
  function grant(target, source) {
    Object.assign(target, source);
  }

  function revoke(target, source) {
    Object.keys(source).forEach(function(key) {
      delete target[key];
    });
  }

  var hasOwn = Object.prototype.hasOwnProperty;

  var shared = {
    message: "the message"
  };

  return {
    invoker: function(foreign) {
      for (var p in foreign) {
        if (hasOwn.call(foreign, p) && typeof foreign[p] === "function") {
          // grant access
          grant(foreign[p], shared);

          // invoke
          foreign[p]();

          // revoke access
          revoke(foreign[p], shared);
        }
      }
    }
  };
}());

var foreign = {
  a: function() {
    console.log("Within a:", this.a.message);
  }
};

Object.defineProperty(foreign, "b", {
  value: function() {
    console.log("Within b:", this.b.message);
  },
  enumerable: true,
  writable: false,
  configurable: false
});


lib.invoker(foreign);
// "Within a: the message"
// "Within b: the message"

console.log( foreign.a.message === undefined );
console.log( foreign.b.message === undefined );
// true
// true