Game Development Reference
In-Depth Information
In this example, you check whether the variable is equal to null (not pointing to an object). If so,
you create a Cannon instance using the new keyword, after which the situation in memory is changed
again (see Figure 11-11 ).
Cannon
anotherCannon
...
Figure 11-11. Final situation in memory
It's up to you to decide when you would like to use null and undefined . Not all programmers do this
the same way. We suggest that you use undefined to indicate that a variable doesn't exist and null
to indicate that the variable exists but doesn't yet refer to any object.
What You Have Learned
In this chapter, you have learned:
How to use inheritance to structure related classes in a hierarchy
How to override methods in a subclass to provide specific behavior for
that class
How to call methods from the superclass, such as the constructor method
null and undefined
The meaning of
 
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