gistfile1.txt

function MyClass(config) {
  this.initialize(config);
}

MyClass.prototype = {
  initialize: function(config) {
    //this is the constructor
    this._foo = config.foo;
  },
  herpDerp: function() {
    console.log(this._foo);
  }
}

myClass = new MyClass({'foo':'bar'});
myClass.herpDerp();