What is the difference between an Array and an ArrayCollection???
The only difference I've noticed is the ability to use the ArrayCollection.addItem(object) method to push object data into the array, but as someone has quite rightly said, could you not simply use Array.push()

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What is a collection?"In object-oriented programming, a collection class is any class that is capable of storing other objects. Collection classes usually implement some kind of data structure, such as a list, map, set, array, or tree. A collection class is usually able to store an arbitrary number of data items, i.e. the size of the collection is adjusted automatically."
Useful article called "What is an ArrayCollection