npm run build is not minifying the reactJs project

Question

I executed the npm command "npm run build" from the reactJs App root folder and "build' folder is generated with the below output in the console.

    File sizes after gzip:

  646.8 KB  build\static\js\2.d370d4e1.chunk.js
  12.46 KB  build\static\js\main.fec451dd.chunk.js
  823 B     build\static\css\main.fc109ae9.chunk.css
  772 B     build\static\js\runtime-main.83c3e0c4.js

The project was built assuming it is hosted at /.
You can control this with the homepage field in your package.json.

The build folder is ready to be deployed.
You may serve it with a static server:

  serve -s build

Then I executed the command "serve -s build" and got the below output in the console.

INFO: Accepting connections at http://localhost:5000

I could see all the *.tsx files not minified in developer tools. Not sure what am I doing wrong and why the files in the below mentioned "js" folder are not minified.

package.json

 {
  "name": "my-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@material-ui/core": "^4.11.0",
    "@material-ui/icons": "^4.9.1",
    "@material-ui/lab": "^4.0.0-alpha.56",
    "@testing-library/jest-dom": "^4.2.4",
    "@testing-library/react": "^9.5.0",
    "@testing-library/user-event": "^7.2.1",
    "@types/jest": "^24.9.1",
    "@types/node": "^12.12.68",
    "@types/react": "^16.9.53",
    "@types/react-dom": "^16.9.8",
    "node": "^15.4.0",
    "react": "^16.14.0",
    "react-dom": "^16.14.0",
    "react-scripts": "3.4.3",
    "typescript": "^3.7.5",
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject",
    "prod": "webpack --mode production"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "devDependencies": {
    "ts-loader": "^8.0.12",
    "typescript": "^3.7.5",
    "webpack-cli": "^4.3.0"
  }
}

Answer 1

The setup is obviously right. The thing you have seen was just the sourcemap which is to map to the source code (for debug purpose) that's why you can search under browser devtool.

Basically sourcemap is generated by default setup of cra in webpack configuration file.

However, if you wish to stop generating it, you can do it via CLI:

package.json

{
  "scripts": {
    // ...
   "build": "GENERATE_SOURCEMAP=false react-scripts build",
    // In case of using Windows:
    "build": "set \"GENERATE_SOURCEMAP=false\" && react-scripts build",
  }
}

Then you would no longer see you code under devtool.

Answer 2

Install the React Developer Tools extension. Hover over the extension if it says you are using production build then your files are minified. As you can see the image below. Also read about production build from official docs from react.

https://reactjs.org/docs/optimizing-performance.html