run-once.md

How to run the code once

React has a built-in hook called useEffect(). This hook runs when the component renders. To ensure the useEffect() only runs once, you can pass the second argument as []:

import React, { useEffect } from 'react';

function App() {
  useEffect(() => {
    // Run! Like go get some data from an API.
  }, []);

  return (
    <div>
      {/* Do something with data. */}
    </div>
  );
}

The second param is an array of variables that the component will check to make sure changed before re-rendering.

References:

• https://css-tricks.com/run-useeffect-only-once/