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I have a brand new project created with:

$ npx create-react-app test-react-app && cd test-react-app && npm start

here the repo: https://github.com/tlg-265/test-react-app

I created a new script: /prepare-project.js with the following content:

let project = 'ferrari' // replace this value with the one passed via: $ npm start [what to put here?]

console.log(`########################`);
console.log(`###### The current project is: ${project} ######`);
console.log(`########################`);

The content of file: /package.json is:

{
  "name": "test-react-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^4.2.4",
    "@testing-library/react": "^9.3.2",
    "@testing-library/user-event": "^7.1.2",
    "react": "^16.12.0",
    "react-dom": "^16.12.0",
    "react-scripts": "3.3.1"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject",
    "prestart": "node prepare-project.js"
  },
  "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"
    ]
  }
}

where you can see I configured the pre hook:

"prestart": "node prepare-project.js"

My goal is to run:

$ npm start [what to put here?]

so inside the script: /prepare-project.js I can read that value.

I tried with:

$ node prepare-project.js --project=mclaren

with no luck when trying to read that value from inside the script: prepare-project.js.

Any idea on how to achieve this?

Thanks!

Viewsonic
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  • why do you want to put that value in a js file and pass to npm script. why don't you just put that in an environment `.env` file – Zohaib Ijaz Feb 02 '20 at 16:16
  • @ZohaibIjaz because that value is not static and will change to whatever random value dynamicly. – Viewsonic Feb 02 '20 at 16:23

1 Answers1

1

You can use yargs module to parse command line arguments and then you can use child_process to execute your command. Here is what your code should look like, you may add your own custom logic.

const yargs = require('yargs');
const { execSync } = require('child_process');

const argv = yargs
    .option('project', {
        alias: 'p',
        description: 'name of the project',
        type: 'string',
    })
    .help()
    .alias('help', 'h')
    .argv;

console.log(argv.project);
console.log(`npm start --project=${argv.project}`);
const output = execSync(`npm start --project=${argv.project}`);
console.log(output)
Zohaib Ijaz
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  • that almost did the trick. When I run: `$ node prepare-project.js -p ford` it works well, but when I run: `$ npm start -p ford` then the script: `prepare-project.js` is not able to read the value of parameter: `project`. Any idea on how to make it work? – Viewsonic Feb 02 '20 at 17:30
  • even when I run: `$ npm run prestart --project=ford` the value of: `project` is `undefined`. – Viewsonic Feb 02 '20 at 17:47
  • use `P=ford npm run prestart` and then access this `process.env.P` – Zohaib Ijaz Feb 02 '20 at 17:59