InternalOptionalanimationManager: AnimationManagerWhether FLIP animations are currently in progress
Set the selector for draggable items
Jump running FLIP animations to their end state
Get sortable items (only elements matching the draggable selector).
The placeholder and the ghost are clones of a real item, so they match
the selector — both are marked with data attributes and excluded here,
otherwise index math counts phantom items (the ghost lives inside the
zone element when fallbackOnBody is false).
Controlled-mode view of the list: draggable items excluding the placeholder (already filtered by getItems), items hidden for the active controlled drag, and any explicitly excluded elements (the dragged items — the HTML5 pipeline leaves them visible in place).
Controlled-mode drop index: the index the dragged item(s) will occupy
in this list AFTER the consumer commits the move — i.e. the count of
visible draggable siblings (see getVisibleItems) before
placeholder.
Get index of an item within container
Insert node before ref (append when null), FLIP-animating the
displaced items. Controlled mode uses this to move the placeholder.
Move item to new index within container (among sortable items only)
Move multiple items to a target index, preserving their relative order
Manages sortable container and basic DOM operations