How am I failing to update a state variable in ReactJS?

Question

I have an event handler in ReactJS designed so that when someone clicks the \"Done\" checkbox for a calendar entry, the calendar entry is still in the system but it is marke

Answer 1

From the documentation (in a big red box nonetheless):

setState() does not immediately mutate this.state but creates a pending state transition. Accessing this.state after calling this method can potentially return the existing value.

and

The second (optional) parameter is a callback function that will be executed once setState is completed and the component is re-rendered.

That callback gets passed the updated state afaik.