title: React - hide and show individual element
body: <p>I am trying to toggle show/hide on individual elements. I thought the key={item._id} will be enough to toggle the individual items, but when clicking the toggle button every element is revealed.  </p>
  
  <p>This is my attempt: <a href="https://codesandbox.io/s/thirsty-torvalds-xnkt1?file=/src/App.js" rel="nofollow noreferrer">https://codesandbox.io/s/thirsty-torvalds-xnkt1?file=/src/App.js</a></p>
  
  <p>I would really appreciate any suggestion. Thanks</p>