foo.js

/**
 *  Self constructing constructor?
 */
 
function Dog (props) {
  if (!(this instanceof Dog)) return new Dog(props);
  this.props = props || {};
};
 
Dog.prototype.bark = function () {
  console.log.apply(console, arguments);
};
 
var fido = Dog({name: 'fido'});
 
fido.bark('I am an annoying dog');