useState.js

import React, { useState } from 'react';

const App = () => {
  const [name, setName ] = useState('')
  const [age, setAge] = useState('')
  const [error, validateForm] = useState({})

  const handleSubmit = () => {
    if(!age || !name) {
      validateForm({message: 'Enter all values'})
    } else {
      validateForm({})
    }
  }

  return (
    <div>
      <div>Name: {name}</div>
      <div>Age: {age}</div>
      <input value={name} onChange={(e) => setName(e.target.value)}/>
      <input value={age} onChange={(e) => setAge(e.target.value)}/>
      <button onClick={handleSubmit}>Submit</button>
      <div style={{color: 'red' }}>
        {error.message}
      </div>
    </div>
  );
}

export default App