Key — Is a special string attribute you need to include when creating lists of elements.

Keys help React identify which items have changed, are added, or are removed.

const numbers = [1, 2, 3, 4, 5];
const listItems = =>
  <li key={number.toString()}>

When you don’t have stable IDs for rendered items, you may use the item index as a key as a last resort.

Key — Structure map

Clickable & Draggable!

Key — Related pages: