Joi -> JSON Schema Converter

Usage no npm install needed!

<script type="module">
  import joiToJsonSchema from '';



The goal is to provide best effort conversion from Joi objects to JSON Schema (draft-04) with the understanding that only some of Joi's schematics can be converted directly. Primarily this module exists to convert Joi schema objects for existing tools which happen to currently consume JSON Schema.

npm version Build Status Dependencies Status DevDependencies Status



npm install joi-to-json-schema


var joi = require('joi'),
    convert = require('joi-to-json-schema'),
    joiSchema = joi.object({
      'name': joi.string().required().regex(/^\w+$/),
      'description': joi.string().optional().default('no description provided'),
      'a': joi.boolean().required().default(false),
      'b': joi.alternatives().when('a', {
        is: true,
        then: joi.string().default('a is true'),
        otherwise: joi.number().default(0)


which will produce:

{ type: 'object',
   { name: { type: 'string', pattern: '^\\w+

     description: { default: 'no description provided', type: 'string' },
     a: { type: 'boolean', default: false },
     b: { oneOf: [ { default: 'a is true', type: 'string' }, { type: 'number', default: 0 } ] } },
  additionalProperties: false,
  required: [ 'name', 'a' ] }


  * Converts the supplied joi validation object into a JSON schema object,
  * optionally applying a transformation.
  * @param {JoiValidation} joi
  * @param {TransformFunction} [transformer=null]
  * @returns {JSONSchema}
 export default function convert(joi,transformer=null) {
   // ...

  * Joi Validation Object
  * @typedef {object} JoiValidation

  * Transformation Function - applied just before `convert()` returns and called as `function(object):object`
  * @typedef {function} TransformFunction

  * JSON Schema Object
  * @typedef {object} JSONSchema


Joi's conditional form, i.e. .when('name',{is:cond,then:joi,otherwise:joi}), is evaluated at runtime and since, from the perspective of the schema, there is no way of knowing what the condition might resolve to, this module takes the position that it should provide all possible resolutions in a JSON Schema oneOf:[] clause.


All tests cases are first checked against expected results and then validated using Kris Zyp's excellent json-schema



Copyright 2014, Mozilla Foundation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.