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.

Answer 1

You could also specify this with a comma delimited list.

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

See Joi documentation on allow(value)

Answer 2

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.