title: Build node.js app using yarn but getting error Command "build" not found
body: <p>This is my package.json file.</p>
  
  <pre><code>{
    "name": "moneymall",
    "version": "1.0.0",
    "description": "A money mall server app.",
    "main": "index.js",
    "author": "Anbu Selvan",
    "license": "ISC",
    "keywords": [],
    "dependencies": {
      "body-parser": "^1.18.3",
      "cors": "^2.8.5",
      "e": "0.0.4",
      "express": "^4.16.4",
      "mysql": "^2.16.0",
      "pug": "^2.0.3",
      "yarn": "^1.15.2"
    },
    "devDependencies": {
      "nodemon": "^1.18.10",
      "react-scripts": "^2.1.8"
    }
  }
  </code></pre>
  
  <p>Run <code>yarn build</code> and get this error.</p>
  
  <blockquote>
    <p>yarn run v1.15.2 error Command "build" not found. info Visit
    <a href="https://yarnpkg.com/en/docs/cli/run" rel="noreferrer">https://yarnpkg.com/en/docs/cli/run</a> for documentation about this
    command</p>
  </blockquote>