Inheritance.js

function extend(parent, child) {
  var proto = {};
  for (fnName in parent.prototype) {
    proto[fnName] = parent.prototype[fnName];
  }
  for (fnName in child.prototype) {
    proto[fnName] = child.prototype[fnName];
  }
  child.super = parent;
  child.prototype = proto;
}

// parent
function Parent(name) {
  this.name = name;
}
Parent.prototype.say = function () {
  console.log('Parent! ' + this.name);
}

// child
function Child(name) {
  Child.super.call(this, name);
}
Child.prototype.say = function () {
  console.log('Child! ' + this.name);
}

extend(Parent, Child);

var parent = new Parent("bob");
parent.say();
console.log(parent);

var child = new Child("ann");
child.say();
console.log(child);