Power Constructors

powerConstructorDefineProperty.js

const instanceCount = 2;

var IHaveThePower = function (passedInConfig) {
  var config = JSON.parse(JSON.stringify(passedInConfig));
  var okForPublic = {'foo':0, 'bar':0};
    
  var exports = {};
  
  function publicize(key) {
    Object.defineProperty(exports, key, {
      get: function () {
        return config[key];
      },
      set: function (value) {
        config[key] = value;
      },
      configurable: true
    });
  }
  
  for(var key in okForPublic) {
    publicize(key);
  }
  
  return exports;
};

var config = {
  foo: 'Foo',
  bar: 'Bar',
  qux: 'Qux',
  Quux:'Quux'
};

var instances = [];

for (var i = 0; i < instanceCount; i++) {
  instances.push(new IHaveThePower(config));
}

config['foo'] = 'foo';

for (var i = 0; i < instanceCount; i++) {
  var instance = instances[i];
  console.log(instance.foo);
}

instances[1].foo = 'foo';

for (var i = 0; i < instanceCount; i++) {
  var instance = instances[i];
  console.log(instance.foo);
}

config['foo'] = 'Foo';

var IAlsoHaveIt = function (config) {
  var exports = IHaveThePower.call(this, config);
  Object.defineProperty(exports, 'foo', {
    value: 'FOO',
    writable: true
  });
  return exports;
};

var alsoInstances = [];

for (var i = 0; i < instanceCount; i++) {
  alsoInstances.push(new IAlsoHaveIt(config));
}

alsoInstances[1].foo = false;

for (var i = 0; i < instanceCount; i++) {
  var instance = alsoInstances[i];
  console.log(instance.foo);
}


/*
  Foo
  Foo
  Foo
  foo
  FOO
  false
 */

powerConstructorGetSet.js

const instanceCount = 4;

var IHaveThePower = function (passedInConfig) {
  var config = JSON.parse(JSON.stringify(passedInConfig));
  var okForPublic = {'foo':0, 'bar':0};
    
  var exports = {};
  
  exports.get = function (key) {
    return (key in okForPublic) ? config[key] : null;
  }
  
  exports.set = function (key, value) {
    (key in okForPublic) ? config[key] = value : void 0;
  }
  
  return exports;
};

var config = {
  foo: 'Foo',
  bar: 'Bar',
  qux: 'Qux',
  Quux:'Quux'
};

var instances = [];

for (var i = 0; i < instanceCount; i++) {
  instances.push(new IHaveThePower(config));
}

config['foo'] = 'foo';

for (var i = 0; i < instanceCount; i++) {
  var instance = instances[i];
  console.log(instance.get('foo'));
}

instances[3].set('foo', 'foo');

for (var i = 0; i < instanceCount; i++) {
  var instance = instances[i];
  console.log(instance.get('foo'));
}

/*
  Foo
  Foo
  Foo
  Foo
  Foo
  Foo
  Foo
  foo
 */