start.js

// @ts-check
// Do not run this file directly. Run it via `npm run watch`. See package.json for more info.
const { spawn } = require('child_process');

/**
 * 
 * @param {string} program 
 * @param {string[]} args 
 * @returns {ReturnType<typeof spawn>}
 */
function cmd(program,  path = "./client", args = [],) {
   if (path) {
      process.chdir(path);
   }
   const spawnOptions = { "shell": true };
   console.log('CMD:', program, args.flat(), spawnOptions);
   const p = spawn(program, args.flat(), spawnOptions); // NOTE: flattening the args array enables you to group related arguments for better self-documentation of the running command
   // @ts-ignore [stdout may be null?]
   p.stdout.on('data', (data) => process.stdout.write(data));
   // @ts-ignore [stderr may be null?]
   p.stderr.on('data', (data) => process.stderr.write(data));
   p.on('close', (code) => {
     if (code !== 0) {
         console.error(program, args, 'exited with', code);
     }
   });
   return p;
}

cmd('node', null, ['test.js']);