4_useContextHooks.js

import React, { useState } from "react";

var userDetailContext = React.createContext(null);

export default function UserDetailsComponent() {
  var [userDetails] = useState({
    name: "Mayank",
    age: 30
  });

  return (
    <userDetailContext.Provider value={userDetails}>
      <h1>This is the Parent Component</h1>
      <hr />
      <ChildComponent userDetails={userDetails} />
    </userDetailContext.Provider>
  );
}

function ChildComponent(props) {
  return (
    <div>
      <h2>This is Child Component</h2>
      <hr />
      <SubChildComponent />
    </div>
  );
}

function SubChildComponent(props) {
  var contextData = React.useContext(userDetailContext);
  return (
    <div>
      <h3>This is Sub Child Component</h3>
      <h4>User Name: {contextData.name}</h4>
      <h4>User Age: {contextData.age}</h4>
    </div>
  );
}

You created all parent child components in single file because of this userDetailContext is available to all child component what if child component is in another file. How will I get userDetailContext there ?