how to process data from form in express code example

Example 1: post express node js input

<form method="POST" action="/submit-form">
  <input type="text" name="username" />
  <input type="submit" />
</form>

Example 2: post express node js input

app.post('/submit-form', (req, res) => {
  const username = req.body.username
  //...
  res.end()
})