package.json：如何测试 node_modules 是否存在

Question

Inside package.json , is it possible to test if node_modules directory exists? My goal is to print a message if node_module does not exists, something like:

node_module not existent: use npm run dist

where dist is a script inside scripts of my package.json. Thank you.

Answer 1

I thought I would post what I've done for cross-platform one-liner conditional NPM scripts.

"scripts": {
    "start":"(node -e \"if (! require('fs').existsSync('./node_modules'))
{process.exit(1)} \" || echo 
'node_module dir missing: use npm run dist') && node start-app.js",
}

Answer 2

Yes it is, via npm scripts . Which npm script to use is your choice. If your application starts via npm start (good practice) use the start script to add your check:

"scripts": { "start": "./test.sh" }

The actual test for the directory can be implemented via a shell script or a NodeJs script, consider using npx as discussed in Difference between npx and npm? .

Answer 3

As suggested by BM in comments, I've created the following script named checkForNodeModules.js :

const fs = require('fs');
if (!fs.existsSync('./node_modules'))
  throw new Error(
    'Error: node_modules directory missing'
  );

And inside my package.json :

"scripts": {
  "node-modules-check": "checkForNodeModules.js",
  "start": "npm run node-modules-check && node start-app.js",
}

Thanks!

Answer 4

With this script I have run yarn install in subfolder app of my project dir (if node_modules not exist)

const fs = require('fs');
const path = require('path');
const spawn = require('cross-spawn');

if (!fs.existsSync(path.resolve(__dirname, '../app/node_modules'))) {
  
  const result = spawn.sync(
    'yarn',
    ['--cwd', path.resolve(__dirname, '../app'), 'install'],
    {
      stdio: 'inherit'
    }
  );
  console.log(result);
}