1.make the backend folder (server.js inside it)

2.in backend npx-create-react-app frontend

package.json  of backend

"scripts": {
   
    "start": "node server.js",
    "frontend":"npm start --prefix ../frontend",
    "dev": "concurrently \\"npm run start\\" \\"npm run frontend\\""

  },

1. start with npm run dev in the backend

FOR VITE ASSSITANCE

package.json in frontend

  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "lint": "eslint . --ext js,jsx --report-unused-disable-directives --max-warnings 0",
    "preview": "vite preview"
  },
  
  it runs by npm run dev

package.json in backend 

  "scripts": {
    "start": "node -r dotenv/config --experimental-json-modules server.js",
    "frontend":"npm run dev --prefix ./frontend",
    "dev": "concurrently \\"npm run start\\" \\"npm run frontend\\""
  },

Your package.json scripts are set up for running a Node.js backend and a frontend (likely React or another JavaScript framework) using concurrently. Here's what each script does:

Explanation of Scripts

"start": "node server.js"