 Returns a copy of the array without null and undefined values.
 
 <code><pre>
-
    [null, undefined, 3, 3, undefined, 5].compact() 
 => [3, 3, 5]
-
 </pre></code>
 
 @name compact

   fullArray.clear()
   fullArray 
=> []

</pre></code>

@name clear

the same objects.

<code><pre>
   a = ["a", "b", "c"]
   b = a.copy()

