getRandomExists(startIndex, endIndex) → {any}
Returns a random child from the Group that has exists set to true. Optionally you can specify a start and end index. For example if this Group had 100 children,and you set startIndex to 0 and endIndex to 50, it would return a random child from onlythe first 50 children in the Group.
Parameters
Name Type Argument Default Description startIndex integer <optional> 0 The first child index to start the search from. endIndex integer <o