Javascript: Module Pattern to define a class

gistfile1.js

// Javascript module pattern to define class
// having private and public members and functions

var Cat = (function() {
    // private member
    var _name = null;
  
    // constructor
    function Cat(name) {
      _name = name;     // this one is private
      this.name = name; // this one is public
    }
  
    // private method
    var _speak = function() { 
      return 'meow';
    };
          
    // public method
    Cat.prototype.speak = function() {
        return 'I say ' + _speak();
    };

    // public method
    Cat.prototype.sayYourName = function() {
        return 'I am ' + _name;
    };

    return Cat;
}());

var cat = new Cat('Alice');
console.log(cat.speak());
console.log(cat.sayYourName());
console.log(cat.name);