Re-usable validation, with optional() and exists()

I have a user route where one can POST (to create a user) or PUT (to edit a user). A user has a username that I want to validate.

In the POST case I want to validate that it exists() In the PUT route I want to validate that it is optional()

But in both routes I want to validate that the username fulfills this part, which I want to re-use:

      .isLength({ min: 1, max: 20 })
      .matches(/^[a-zA-Z0-9][a-zA-Z0-9-_]*$/)
      .withMessage('Username can only contain a-zA-Z0-9-_')

I do not know how to achieve this, with re-usability, considering the .optional() and .exists() should come first in those two validation chains.

[fedeci]

This is something we should definitely implement because the same problem also happened to me. You may resolve with some kind of wrapper around checkSchema. (Keep also in mind that if you want to edit partially an entity you should use PATCH instead of PUT.) /cc @gustavohenke

[fedeci]

• @fedeci that means if I use a factory function to create a chain like explained here https://express-validator.github.io/docs/validation-chain-api.html, then I can just call that and add .optional() to the end in the PATCH route? To be explicit (not complete example, being lazy):

// factory function

usernameFactoryChain = () => {

      return body('username').

      .isLength({ min: 1, max: 20 })

      .matches(/^[a-zA-Z0-9][a-zA-Z0-9-_]*$/)

      .withMessage('Username can only contain a-zA-Z0-9-_')

}



app.patch('users/', usernameFactoryChain(), ...);

app.patch('users/', usernameFactoryChain().optional(), ...);

Then I do not understand anymore what needs to change, if that works? 😄

Does this solve the issue for you @jatinmehrotra?