testing object and prototype

1. Create an object called shape that has the type property and a
getType() method.

2. Defne a Triangle() constructor function whose prototype is shape. Objects
created with Triangle() should have three own properties—a, b, and c,
representing the lengths of the sides of a triangle.

3. Add a new method to the prototype called getPerimeter().

4. Test your implementation with the following code:

var t = new Triangle(1, 2, 3);
t.constructor === Triangle; //true
shape.isPrototypeOf(t); //true
t.getPerimeter(); //6
t.getType(); //"triangle"

5. Loop over t showing only own properties and methods (none of
the prototype’s).

6. Make the following code work:

[1, 2, 3, 4, 5, 6, 7, 8, 9].shuffle(); // [2, 4, 1, 8, 9, 6, 5, 3, 7]

Nguồn: Object-oriented JavaScript (S.Stefanov, page 170)