how to child process node how to send message code example

Example 1: node spawn

const { spawn } = require('child_process');
const ls = spawn('ls', ['-lh', '/usr']);

ls.stdout.on('data', (data) => {
  console.log(`stdout: ${data}`);
});

ls.stderr.on('data', (data) => {
  console.error(`stderr: ${data}`);
});

ls.on('close', (code) => {
  console.log(`child process exited with code ${code}`);
});

Example 2: how to return when child process is complete in node js

var execSync = require('exec-sync');

var user = execSync('python celulas.py');