joi custom validation depending on other field's data

I am trying to create a custom validation rule (using the JOI validations library in a node.js application) that dependent of other fields of the form.

For example: I need the username field to be required if both of the email or mobile fields are empty or visa versa.

I have already tried the when and or methods, provided by the library itself and searched on the google as well. But, still standing on same place.

When example:

const validations = joi.object({
    ...
    username: joi.any().when('email', {
        is: '' || null || undefined,
        then: joi.required()
    }),
    email: joi.any().optional(),
    mobile: joi.any().optional(),
    ...
}).options({
    abortEarly: false
});

Or Example:

const validations = joi.object({
    ...
    username: joi.any(),
    email: joi.any(),
    mobile: joi.any(),
    ...
}).or('username', 'email', 'mobile').options({
    abortEarly: false
});

Please help, this issue has already cost me too much time.

Here is my working code:

Reference: https://stackoverflow.com/questions/58425499/how-to-add-custom-validator-function-in-joi/61638633#64233670

export default (req, res, next) => {
    const validations = joi.object({
        ...
        email: joi.any().custom((value, helper) => {
            if (! value && ! req.body.username && ! req.body.mobile) {
                return helper.message('Required field');
            }

            return true;
        }),
        mobile: joi.any().custom((value, helper) => {
            if (! value && ! req.body.username && ! req.body.email) {
                return helper.message('Required field');
            }

            return true;
        }),
        username: joi.any().custom((value, helper) => {
            if (! value && ! req.body.email && ! req.body.mobile) {
                return helper.message('Required field');
            }

            return true;
        }),
        ...
    }).options({
        abortEarly: false
    });

    const { error } = validations.validate({
        ...
        email: body.email ? body.email : null,
        mobile: body.mobile ? body.mobile : null,
        username: body.username ? body.username : null,
        ...
    });

    if (error) {
        return res.status(406).send({ ... });
    }

    next();
}

I hope this can help someone, facing the situation like this.