3 name: options-onloading
6 The onLoading parameter is called when the tree data is loading. This gives us the opportunity to display a loading signal.
8 Callback looks like this:
11 function (is_loading, node, $el)
14 * **is_loading**: boolean
15 * true: data is loading
16 * false: data is loaded
18 * Node: if a node is loading
19 * null: if the tree is loading
21 * if a node is loading this is the `li` element
22 * if the tree is loading is the `ul` element of the whole tree