Why is useState not triggering re-render?

Question

I\'ve initialized a state that is an array, and when I update it my component does not re-render. Here is a minimal proof-of-concept:

function App() {
  const         


        

Answer 1

You're calling setNumbers and passing it the array it already has. You've changed one of its values but it's still the same array, and I suspect React doesn't see any reason to re-render because state hasn't changed; the new array is the old array.

One easy way to avoid this is by spreading the array into a new array:

setNumbers([...old])