Example code demonstrating the relationship between the prototype and the objects instance values.
You can see that after explicitly setting the value of wheelCount to 4, it retains it's own value even after the prototype value is changed. The new prototype value of 18 applies to the new vehicle2 instance however.
Based on code from the post on "JavaScript constructors, prototypes, and the new
keyword" by Pivotal Labs.
@dfkaye pointed out a bug with the last revision of my code above where the last example referred to vehicle2, not vehicle3