npm install in subfolders recursively

postinstall.js

const fs = require('fs');
const os = require('os');
const childProcess = require('child_process');
const path = require('path');
const walk = function (dir, done) {
  let results = [];
  fs.readdir(dir, function (err, list) {
    if (err) return done(err);
    let i = 0;
    (function next() {
      let file = list[i++];
      if (!file) {
        return done(null, results);
      }
      file = path.resolve(dir, file);
      fs.stat(file, function (err, stat) {
        if (stat && stat.isDirectory()) {
          walk(file, function (err, res) {
            results = results.concat(res);
            next();
          });
        } else {
          results.push(file);
          next();
        }
      });
    })();
  });
};

walk(path.resolve(__dirname, 'static'), function (err, results) {
  if (err) throw err;

  results.forEach((fileSrc) => {
    if (fileSrc.endsWith(path.sep + 'package.json') && !/node_modules/.exec(fileSrc)) {
      const filePath = fileSrc.replace(path.sep + 'package.json', '');

      console.log('===================================================================');
      console.log(`Performing "npm install" inside ${filePath}`);
      console.log('===================================================================');

      const npmCmd = os.platform().startsWith('win') ? 'npm.cmd' : 'npm';

      childProcess.spawn(npmCmd, ['i'], {
        env: process.env,
        cwd: filePath,
        stdio: 'inherit',
      });
    }
  });
});