Joi: Joi undefined

[sm2017]

Context

• node version: 10.14.2
• joi version:14.3.1
• environment (node, browser):node
• used with (hapi, standalone, ...):standalone
• any other relevant information:---

What are you trying to achieve or the steps to reproduce ?

const schema = Joi.object({
    a: Joi.string().default('a'),
    b: Joi.string()
})

const input = undefined;
const result = Joi.validate(input,schema);
console.log(result)

Which result you had ?

result is undefined

What did you expect ?

result must be {a:'a'}

[WesTyler]

As it's written, the default will only be applied if the value is an object, but the a property is empty:

const schema = Joi.object({
    a: Joi.string().default('a'),
    b: Joi.string()
})

const input = {};
const result = Joi.validate(input,schema);
console.log(result) // value: { a: 'a' }

If you want this to work for an undefined input for the object you'll need the default on the object itself:

const schema = Joi.object({
    a: Joi.string(),
    b: Joi.string()
}).default({ a: 'a' });

const input = undefined;
const result = Joi.validate(input,schema);
console.log(result); // value: { a: 'a' }

[sm2017]

@westyler so I have to define default twice , and when my object has too many fields its very tedious

[WesTyler]

If you want to stamp in defaults for undefined for both the parent object
and also the children, then yes. Though you can simplify it with some
schema composition (I can elaborate when I get back to a computer this
evening).

On the note about it being tedious, think about the alternative without
leveraging Joi’s default handling. You would have to check the parent and
then default to an object, then manually write conditional checks for each
field. I personally think that verbose schema are more clear and easily
maintained, but don’t feel like you have to leverage Joi for all of your
business logic :)

On Mon, Jan 21, 2019 at 11:30 AM sm2017 [e-mail] wrote:

@WesTyler https://github.com/WesTyler so I have to define default twice
, and when my object has too many fields its very tedious

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[Marsup]

Default has a special case for objects where you can call it without any argument and it will do what you want.

[sm2017]

@Marsup your approach works , But I have another issue

var Joi = require("joi")
const schema = Joi.object({
    a: Joi.string().default('a'),
    b: Joi.string()
}).default()

const input = undefined;
Joi.validate(input,schema,function(err,value){
   console.log('err',err)
   console.log('value',value)
});

is OK and we have default values for undefined , But I want to extend Joi and

params: { options: Joi.object({
        a: Joi.string().default('a'),
        b: Joi.string()
    }).default()
 }

is not works and default is not set

[Marsup]

params can also be a Joi.object itself.

[Marsup]

Considering it solved, let me know if not.

[lock[bot]]

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