onBeforeAdd

fires before adding an item to the datastore

boolean onBeforeAdd(string|number id,object obj,number index);

id	string\|number	the ID of the newly added data item
obj	object	data for the new item
index	number	the index, at which the new item will be added

boolean

false, if the operation needs to be cancelled

view.data.attachEvent("onBeforeAdd", function(id, obj, index){
    if (obj.text == "")
        return false;
});

Details

Returning false from the event handler will block further processing, and the item will not be added.