Understanding unique keys for array children in React.js

Question

I\'m building a React component that accepts a JSON data source and creates a sortable table.
Each of the dynamic data rows has a unique key assigned to it but I\'m stil

Answer 1

Check: key = undef !!!

You got also the warn message:

Each child in a list should have a unique "key" prop.

if your code is complete right, but if on

someValue is undefined!!! Please check this first. You can save hours.