gistfile1.js

//extending the object prototype
Object.prototype.newMethod = function() {
   return this;
};

//create new Object
var names = {'Jane': 'Joe', 'John': 'Doe'};

//iterating the Object would give: Jane => Doe, John => Doe, newMethod => function();
for(var key in names) {
   console.log(key, '=>', names[key], ',');
}

//thats why object.hasOwnProperty should be called on each iteration. 
//It checks whatever key exists on object itself not it prototypes chain.
//iterating the Object would give: Jane => Doe, John => Doe,
for(var key in names) {
   if (names.hasOwnProperty(key)) {
       console.log(key, '=>', names[key]);
   }
}