How do I show a HTML tag only when Express view engine passes a value?

Question

If you see the code below, you'll notice that for GET request, 'add' page does not get any value passed, whereas for POST request, 'add' page gets 'msg' value as a result of posting.

router.get('/add', (req, res) => {
  res.render('add', {})
})

router.post('/add', (req, res) => {
  // receive a form 
  // save it to the database
  // Promise is returned
  .then(gig => res.render('add', {
    msg: 'Your application is successful.'
  })
  .catch((err) => console.log(err));
  }
 })

In add.ejs file, I am not allowed to write <%= msg %> because it will cause an error for GET requests. Is there any other way than passing a { msg: null } to the GET router?

router.get('/add', (req, res) => {
      res.render('add', { msg: null })
})

I'm asking this because I think passing null for cases like this is very repetitive.

Answer 1

the alternative would be adding a control in the file you want to render

<% var msg = msg ?? null %>

this way if the variable msg isn't passed the value is null and the field will be empty