In all programming languages that sport object oriented features there is a concept known as "Inheritance". Inheritance is when an object inherits all of the properties and methods of its parent object, to become a specialized version of the parent object. In JavaScript we use the prototype property to establish subclasses that inherit the characteristics of our parent classes. This results in a specialized subclass that can retain its own properties and methods, as well as inherit all of the properties and methods of the parent class. <script> // Establish a parent class function Parentclass(){ this.parent_property1 = "Hola"; this.parentmethod1 = function parentmethod1(arg1){ return arg1+" Parent method 1 return data ..."; } } // Establish a child class function Childclass(){ this.child_property1 = "Adios"; this.childmethod1 = function childmethod1(arg1){ return arg1+" Child method 1 return data ..."; } } // Make the Childclass inherit all of the Parent class characteristics // by using the prototype property, explained in depth here: youtube.com/watch?v=EBoUT2eBlT4 Childclass.prototype = new Parentclass(); // Create a new instance of Childclass var instance1 = new Childclass(); // Check to see if instance1 is an instance of both objects alert( instance1 instanceof Parentclass ); alert( instance1 instanceof Childclass ); // Access the instance methods and properties alert( instance1.parentmethod1("RESULT: ") ); alert( instance1.childmethod1("RESULT: ") ); alert( instance1.parent_property1 ); alert( instance1.child_property1 ); // Override parentmethod1 in the Childclass Childclass.prototype.parentmethod1 = function parentmethod1(arg1){ return arg1+" I have overridden Parent method 1"; } alert( instance1.parentmethod1("RESULT: ") ); </script>