Nested noChange() Joi Validation

nested-noChange.js

var validate = require('json-patch-joi');
var Joi = require('joi');

function clone(obj) { return JSON.parse(JSON.stringify(obj)); }

// original object to be patched
let obj = { nested: { stuff: true } };

// patch that illegally modifies the stuff value
const patch = [{
    op: 'replace',
    path: '/nested/stuff',
    value: 'something else'
}];

// With the use of "noChange()", validating bad patches is easy
const schema = Joi.object().keys({
    nested: Joi.object().keys({
        stuff: Joi.any().noChange(obj)
    })
});

// Joi validation error object in res.error
const res = validate(clone(obj), schema, patch);
// `res.error.message`: child "nested" fails because [child "stuff" fails because ["stuff" is not allowed to be changed]]