[Fixed] Express/MongoDB – How to use res.render inside a try/catch block when sending requests to a databse

Issue

I’m making a poll app, and one of my routes is a GET request to get all the polls.

All i want to do is pass the polls to my dashboard view, and if there are no polls I want to pass the error to the dashboard view also.

I think my current implementation is wrong because if there are no polls the dashboard view receives an empty array not the errors.

I was curious what the best approach would be in this situation.

Thanks

router.get('/dashboard', isAuth, async (req, res) => {
    try {
        const polls = await Poll.find().populate('user', ['name', 'id']);
        
        res.render('dashboard', {
            polls
        });
    } catch(err) {
        res.status(400);
        res.render('dashboard', {
            error: 'Could not find any polls'
        });
    }
});

Solution

You can throw error if polls is falsy/empty. Like this this:

const getType = element => Object.prototype.toString.call(element);

// Put this function in a helper file and use it throughout the source code
const isEmpty = element => {
  if (
    // undefined
    typeof element === 'undefined' ||
    // string
    (typeof element === 'string' && element.trim().length == 0) ||
    // null
    getType(element) === '[object Null]' ||
    // object
    (getType(element) === '[object Object]' && !Object.keys(element).length) ||
    // array
    (getType(element) === '[object Array]' && !element.length)
  ) {
    return true;
  }

  return false;
}

router.get('/dashboard', isAuth, async (req, res) => {
  try {
    const polls = await Poll.find().populate('user', ['name', 'id']);

    if (isEmpty(polls)) {
      throw new Error("Could not find any polls");
    }

    res.render('dashboard', {
      polls
    });
  } catch (err) {
    res.status(400);
    res.render('dashboard', {
      error: 'Could not find any polls'
    });
  }
});