title: If React props are readonly, how they can change (whats the usage of getDerivedStateFromProps)?
body: <p>I'm learning React. I learned that props in react are readonly.</p>
  
  <p>But i read somewhere:</p>
  
  <blockquote>
    <p>getDerivedStateFromProps updates the state based on prop changes</p>
  </blockquote>
  
  <p>So i got confused. If props are readonly, how they can change?</p>