Extending Objects in jQuery
Again, remember that the last one in wins. It is also worth noting that anything extended with an explicit `undefined` will keep its original value. If you want to override a value with a “falsy” value, use `null`, `false` or anything else that makes sense in your case.
Arrays are always overwritten by the last object passed in. The objects inside them are at mercy of their parents. It doesn’t matter if they are values or objects, the last object passed in, gets the last call.
For more information: http://api.jquery.com/jQuery.extend/