Good day dear webix community members.
Can you please avdice me how can i check child items in datatree node?
Methods checkAll\uncheckAll does not work 
checkAll is the necessary API
Check the next example http://webix.com/snippet/c702adfe
If you are loading data by ajax, be sure that you are calling API after data loading ( onAfterLoad event or loading callback )
Thank you for your comment, but this is not quite i’m looking for.
Is it possible to mark all child nodes checked when checking parent?
Like Node4 at this picture:
I’m using OnItemCheck event, and if i’ll use checkAll method application goes into infinite loop.
Do you mean, something like 3-state checkboxes?
Yes, this is absolutely perfect, thank you.