form-state.jsx

import React from "react"

export const MyFormWithState = (props) => {
  const [formState, setFormState] = useState({
    name: "",
    age: 0,
  })
  
  const onChange = (event) => 
      setFormState({
        ...formState,
        [event.currentTarget.name]: event.currentTarget.value,
      })
  
  return (
    <form onSubmit={props.onSubmit}>
      <fieldset>
        <label htmlFor="name">Name</label>
        <input
          onChange={onChange}
          name="name"
          type="text"
          value={formState.name}
         />
        
        <label htmlFor="age">Age</label>
        <input
          onChange={onChange}
          name="age"
          type="number"
          value={formState.age}
         />
      </fieldset>
    </form>
  )
}