Want to add new property or object

[Aman290]

Actually, I am using template and in which I want to pass one more property in TreeviewItem like group true or false as -

new TreeviewItem({ text: 'Name, value: 1, checked: false, group: true });

but it is giving an error Object literal may only specify known properties, and 'group' does not exist in type 'TreeItem'. How can I use some other properties in TreeviewItem?

[andreElrico]

strongly linked to my issue of today #244. I suggest closing #242 into #244.