encapsulation-in-javascript.js

gist-1.js

function Mammal(species, defining_characteristic) {
  this.species = species;
  this.defining_characteristic = defining_characteristic;
 }

Mammal.prototype.print = function(){
  return "Hello I'm a " + this.species + ". " +
         "I have " + this.defining_characteristic + "."
}

var cat = new Mammal("Cat", "claws");
var dog = new Mammal("Dog", "a wet nose")

console.log(cat.print());
// "Hello I'm a Cat. I have claws."

console.log(dog.print());
// "Hello I'm a Dog. I have a wet nose."

gist-2.js

var Mammal = (function(){
  // These are private
  var species;
  var defining_char;
  return {
  // These are public because of the explicit return
        init: function (sp, dc) {
          species = sp;
          defining_char = dc;
        },
        print: function() {
          return "Hello I'm a " + species + ". " +
                 "I have " + defining_char + ".";
        }
      };
});

// cat = Mammal(); cat.init("Cat", "claws"); cat.print();
// "Hello I'm a Cat. I have claws."

// dog = Mammal(); dog.init("Dog", "a wet nose"); dog.print();
// "Hello I'm a Dog. I have a wet nose."