hooks run a code after mounted code example

Example 1: useeffect only on mount

import React, { useEffect } from 'react';

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

Example 2: useeffect componentdidmount

import React, { useState, useEffect } from 'react';
function Example() {
  const [count, setCount] = useState(0);

  // Similar to componentDidMount and componentDidUpdate:  
  useEffect(() => {    
    // Update the document title using the browser API    
    document.title = `You clicked ${count} times`;  
  });

  );
}