[Solved]-Helper function reactjs-Reactjs

// Component 
[...]
return (
    <input
        type="text"
        name="firstName"
        value={form.firstName}
        onChange={event => setForm(assignValueToName(form, event))}
    />
)

// Helper
function assignValueToName(existing, event) {
    const { name, value } = event.target;
    
    return {...existing, [name]: value};
}

//myCustomForm.js

import { useState } from "react";

export default (defaultState) => {
  const [formState, setFormState] = useState(defaultState);

  const handleChange = ({target}) => {
    const { name, value } = target;
    setFormState({
      ...formState,
      [name]: value
    });
    console.log(formState);
  };

  return [formState, handleChange];
};