import React, { useEffect, useState } from 'react'; function App() { const [age, setAge] = useState(0); updateAge(value) { setDisplayUsaStudents( (prevDisplayUsaStudents) => !prevDisplayUsaStudents ); setAge({prevAge: value}); }; useEffect(() => { if (age !== 0 && age >= 21) { // Make API call to /beer } else { // Throw error 404, beer not found } //the square parentheses with the age state variable inside is called the dependency array. //it tells the useEffect function to listen for any changes to the state of age. //when age changes, useEffect executes }, [age]); return ( <div> <p>Drinking Age Checker</p> <input type="number" value={age} onChange={e => setAge(e.target.value)} /> </div> ); } export default App;