Uncaught TypeError: e[n].forEach is not a function

[Clementol]

Uncaught TypeError: e[n].forEach is not a function
The main tree is working but to show the children is the problem following the example at npm website

Expected to show sub tree
I expected drop down to show

[WBucci]

Im getting the same issue, but someone on my team has it working. Copying his code doesnt resolve my issue

[jakezatecky]

Can you link to a live version which shows this issue, using this CodeSandbox reference point as a base?

[glxdsunname]

i got this issue when i use hooks in checked and expanded: checked => setChecked( { checked }).
remove "{" and "}" work for me : checked => setChecked( checked ).

[jakezatecky]

That is possible error others may be experiencing. The checked, expanded, and nodes property should all be Arrays.

[jakezatecky]

Since the docs all reference functional/hook usage now, this should no longer be confusing to developers without class experience.