how to use psql in node js code example

Example: node js postgresql query

// callback
client.query('SELECT NOW() as now', (err, res) => {
  if (err) {
    console.log(err.stack)
  } else {
    console.log(res.rows[0])
  }
})
// promise
client
  .query('SELECT NOW() as now')
  .then(res => console.log(res.rows[0]))
  .catch(e => console.error(e.stack))