The tree has the builtin lazy loading functionality. Please look at this example.
https://www.jeasyui.com/demo/main/index.php?plugin=Tree&theme=material-teal&dir=ltr&pitem=Async%20Tree&sort=ascIf you are using the combotree component, please call this line to show the loading icon.
$('#ct').next().find('.combo-arrow').addClass('pagination-loading');
<input id="ct" class="easyui-combotree" ...>