test.js

import React, { useState } from "react";
import "./styles.css";

export default function App() {
  const [data, setData] = useState([
    {
      id: "1",
      itemName: "Item 1",
      color: "blue",
      subitens: [
        {
          id: "1.1",
          subItemName: "Subitem 1.1",
          type: "1"
        },
        {
          id: "1.2",
          subItemName: "Subitem 1.2",
          type: "1"
        }
      ]
    },
    {
      id: "2",
      itemName: "Item 2",
      color: "blue",
      subitens: [
        {
          id: "2.1",
          subItemName: "Subitem 2.1",
          type: "1"
        },
        {
          id: "2.1",
          subItemName: "Subitem 2.2",
          type: "1"
        }
      ]
    }
  ]);
  return (
    <div className="App">
      {data.map(item => (
        <>
          <h1 key={item.id}>{item.itemName}</h1>
          <div>
            {item.subitens.map(subitem => (
              <h2 key={subitem.id}>{subitem.subItemName}</h2>
            ))}
          </div>
        </>
      ))}
    </div>
  );
}