I’ve found a weird behavior when trying to check for a falsy value. I guess it is related to the parser across the HTTP. All values inserted (eg http://www.localhost:3000/knex/0) are converted into strings: falsy values like 0 or ” are converted into “0” and “”” respectively. Therefore, when trying to check for falsy values doesn’t raise an error.

May I be doing something wrong or is it something related to the library ?

My express-validator version: ^7.1.0

I left an example to test it:

const { body, validationResult, checkSchema, param } = require('express-validator');


const customChecker = (value) => {
  console.log('ncustom');
  console.log((value));
  console.log(Boolean(value));
  //if (value === 0) {console.log(value)}
  if (value === '') {console.log(value)}
  if (!Boolean(value)) {
    throw new Error('Invalid id values. custom func');
  } else {
    return true;
  }
}

const idSchema = {
  id: {
    //in: ['params'],
    notEmpty:{errorMessage: "Not id provided"},
    custom: { options: value => customChecker(value) },
    //exists: { options: { values: 'falsy' } }
  }
}


const validateId = [
 // param('id').notEmpty().withMessage('ID is required'),
 checkSchema(idSchema),

  (req, res, next) => {
    const VALRES = validationResult(req);
    if (!VALRES.isEmpty()) {
      return res.status(400).json({ errors: VALRES.array() });
    }
    next();
  }
];


module.exports = { validateId };

app.get('/knex/:id',validateId, async (req, res) => {
  try {
    const item = await knex('tablename').where({ id: req.params.id });
    res.json(item); 
  } catch (error) {
    console.error('ERROR:', error);
    res.status(500).json({ error: 'Internal Server Error' }); 
  }
});