Put

const jquery-validation = require('jquery-validation');

at the top of your app.js

They are used for different scenarios:

• validator is a library to validate any kind of object and it's not associated with any framework.

• express-validator uses validator library to validate expressjs routes. Basically you can validate express routes out of the box using validator lib.

In my honest opinion you can easily create your own validator middleware. Specially if you are new to Node.js it will help you to understand how middlewares work. If you are not interested on that and you have an express application feel free to use express-validator

Also I really recommend JOI as a validator lib https://github.com/hapijs/joi it's simple and it works well.

Here is an example of a middleware (I have not tested)

const Joi = require('joi')
module.exports = function validate(joiSchema) {
  return async (req, res, next) => {
    const result = Joi.validate(req.body, joiSchema, {
      allowUnknown: true,
      abortEarly: false
    })

    if (result.error) {
      throw new result.error
    }

    await next()
  }
}

  // express route
  router.post(
    '/create',
    validateMiddleware({
      body: {
        body: { firstName: Joi.string(), lastName: Joi.string() }
      }
    }),
    (req, res, next) => {
    // your logic
   })

Ignore those. They are benign warnings and don't pertain to you as a user of the validator module. The author of the validator module could fix them by correcting it's package.json file. Not sure why NPM prints these here as they are mostly a nuisance to npm users and they are really messages for package authors.