Allow string to be null or empty in joi and express-validation

Question

I am using "joi": "10.0.6" and "express-validation": "1.0.1" in my project to validate a JSON object which I will save in the DB. One of the field is a string but it could be null or empty. How can I allow my string to pass the validation in the cases it is empty or null?

I have already tried these cases:

dataId: Joi.string().allow(null).allow('').optional()

and

dataId: Joi.alternatives().try(Joi.string(), Joi.allow(null))

but both them don't work.

score 90 · Answer 1 · answered Mar 30 '18 at 21:07

90

You could also specify this with a comma delimited list.

dataId: Joi.string().allow(null, '')

See Joi documentation on allow(value)

answered Mar 30 '18 at 21:07

What Would Be Cool

6,204
5
45
42

I try to do the same using Express-validator/validator.js, any idea how to check for null and validates this correctly? https://github.com/chriso/validator.js https://github.com/express-validator/express-validator – Melroy van den Berg Apr 21 '18 at 21:16
I haven't used that library before, but looks like you could do so with a custom validator. https://github.com/express-validator/express-validator#customvalidator – What Would Be Cool Apr 22 '18 at 22:52
Yea I though the same, however the docs says: "Returns: the current validation chain instance". But I can't return 'null', since Express validator says it can't return null :S. – Melroy van den Berg Apr 24 '18 at 21:29

score 28 · Answer 2 · answered Feb 23 '19 at 19:35

It's very simple, suppose the field is data then you could impose the validation as

data: Joi.string().allow('')

allowing empty string to pass, for multiple string validation it could also be done as

data: Joi.string().allow('', null)

allowing both empty as well as null value for the data field to pass.

score 8 · Answer 3 · answered Apr 05 '21 at 14:10

8

If you want to allow the empty string and treat it the same as undefined (i.e., convert it to undefined), then use Joi's empty method:

data: Joi.string().empty('')

answered Apr 05 '21 at 14:10

Josh Kelley

56,064
19
146
246

score 5 · Answer 4 · answered Mar 19 '17 at 18:41

5

Joi.string().allow('').allow(null) should have worked. I tested locally and it works fine.

Show your test cases and errors?

answered Mar 19 '17 at 18:41

Dao Lam

2,837
11
38
44

Marc · Answer 5 · 2017-02-21T15:25:05.003

4

If you just specify it as

dataId: Joi.string()

it should be optional per default.

EDIT: Could not try it on my own currently. Here an alternative, if above does not work:

dataId: Joi.string().min(0).allow('').allow(null)

edited Feb 21 '17 at 15:25

answered Feb 21 '17 at 15:13

Marc

1,900
14
22

Poçi · Answer 6 · 2021-02-23T16:19:16.340

3

If you need only null or empty string use this:

 dataId: Joi.string().valid(null, '')

edited Feb 23 '21 at 16:19

answered Feb 15 '21 at 09:38

Poçi

243
3
8

Allow string to be null or empty in joi and express-validation

6 Answers6