CreateJS Z-Index

Implements z-index to the children in a container.

Adds a zIndex property to the createjs.DisplayObject object, and a enableZIndex property to createjs.Container object. By default, the enableZIndex property value is true, so whenever another Display Object/child is added to that Container it will sort by the zIndex value. The lower this zIndex value is, the further in the background it will be placed (be drawn first).

If two Display Objects have the same zIndex it will compare their id property value. This id property value is set every time an instance of the Display Object is instantiated, and incremented everytime a new Display Object is created. For example, if you have created two sprites, the first sprite created would have an id of 1, and the second would have an id of 2, respectively. So if both of these sprites have the same zIndex value the first sprite will be drawn then the second.