Joi: Trying to get default value for null or empty for joi.string()

[wbickelmann]

I want a default value for a Joi object if the value is empty or null

config(Joi) { 
       return Joi.object({ 
         enabled: Joi.boolean().default(true), 
         url: Joi.string().allow('').allow(null).default("xyz"),
         jsFilterFunction: Joi.string.allow('').allow(null).default("abc")
       }).default(); 
     }

Trying the above code gives me the following error.

TypeError: Joi.string.allow is not a function

[Edited by Wes to add the code block formatting]

[WesTyler]

You have a typo in your jsFilterFunction property

It should be Joi.string().allow('') instead of Joi.string.allow('') (missing the string method call parens).

[WesTyler]

Aside from that, your general approach should be fine. You shouldn't need the .default() on the object().default() call though.

const schema = Joi.object({
    enabled: Joi.boolean().default(true),
    url: Joi.string().allow('', null).default('xyz'),
    jsFilterFunction: Joi.string().allow('', null).default("abc")
});

schema.validate({});
// value: { enabled: true, url: 'xyz', jsFilterFunction: 'abc' }

[WesTyler]

If you are also wanting your url and jsFilterFunction properties to stamp in the default values when null or '' are present, you'll need to modify each property from:

Joi.string().allow('', null).default('xyz')

to

Joi.string().allow('', null).empty(['', null]).default('xyz')

let schema = Joi.string().allow('', null).default('xyz');

schema.validate(null);
// value: null

schema = Joi.string().allow('', null).empty(['', null]).default('xyz');
schema.validate(null);
// value: 'xyz'

[Marsup]

Without the allow but yes, use empty. Case closed I think.

[rahullad89]

Worked for me Thanks @WesTyler

[lock[bot]]

This thread has been automatically locked due to inactivity. Please open a new issue for related bugs or questions following the new issue template instructions.