<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<p>The value of myFather.nationality is "undefined", because you cannot add a new property to a prototype the same way as you add a new property to an existing object.</p></p>
<script>
function Person(first, last, age, eye) {
this.firstName = first;
this.lastName = last;
this.age = age;
this.eyeColor = eye;
}
Person.nationality = "English";
var myFather = new Person("John", "Doe", 50, "blue");
var myMother = new Person("Sally", "Rally", 48, "green");
document.getElementById("demo").innerHTML =
"My father is " + myFather.nationality;
</script>
</body>
</html>