function ClassA() {
    // Superclass defines a string and a function as static
    ClassA.prototype.str1 = "String 1 from ClassA<br />";
    ClassA.prototype.func1 = function() {
        document.write("Function 1 from Class A<br />");
    };
}

function ClassB() {
    // Subclass defines a string as statisc
    ClassB.prototype.str2 = "String 2 from ClassB<br />"
}

// ClassB inherits all members of ClassA
ClassB.prototype = new ClassA();
// Add more stuff to subclass B after changing its prototype
// because otherwise class instance stuff will be replaced when changing its
// prototype.

// Create an instance of ClassB that has inherited from superclass
var instance = new ClassB();

// Write member variables and functions
document.write(instance.str1);
document.write(instance.str2);
instance.func1();