npm ERR! Missing script: "build" for firebase code example

Example: npm run build npm ERR! Missing script: "build" for firebase

"scripts": {
    "build": "",
    "serve": "firebase serve --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  }