Dynamic JSON Schema Validator - Supports draft-04/06
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Dynamic JSON-Schema Validator

Official Documentation

Current package supports JSON-Schema v6 and v4. It contains utils to validate objects against schemas. This is a part of djv packages aimed to work with json-schema.

  • djv validate object against schemas
  • djvi instantiate objects by schema definition
  • jvu utilities for declarative, FP usage
  • @djv/draft-04 environment updates to support draft-04

Any contributions are welcome. Check the contribution guide. Since version 1.2.0 djv package supports draft-06. Version 2.0.0 makes draft-06 the default schema version. To use other versions check the environment section.

Table of contents


npm install djv


<script src="djv.js"></script>

There are 2 versions of validator

  • ./lib/djv.js a default one, not uglified and not transpiled
  • ./djv.js a built one with a webpack, babel and uglify (preferrable for frontend)


const env = new djv();
const jsonSchema = {
  "common": {
    "properties": {
      "type": {
        "enum": ["common"]
    "required": [

// Use `addSchema` to add json-schema
env.addSchema('test', jsonSchema);
env.validate('test#/common', { type: 'common' });
// => undefined

env.validate('test#/common', { type: 'custom' });
// => 'required: data'



To instantiate djv environment

const djv = require('djv');
const env = djv({
  version: 'draft-06', // use json-schema draft-06
  formats: { /*...*/ }, // custom formats @see #addFormat
  errorHandler: () => { /*...*/ }, // custom error handler, @see #setErrorHandler

To use a previous version of JSON-Schema draft, use a draft-04 plugin, specified in optionalDependencies of djv package.

const env = new djv({ version: 'draft-04' });

addSchema(name: string, schema: object?) -> resolved: object

Add a schema to a current djv environment,

env.addSchema('test', jsonSchema);
/* => {
  fn: function f0(data){...}
  name: 'test'
  schema: ...
} */

validate(name: string, object: object) -> error: string

Check if object is valid against the schema

env.validate('test#/common', { type: 'common' });
// => undefined

env.validate('test#/common', { type: 'custom' });
// => 'required: data'


  • name - schema path in current environment
  • object - object to validate
  • error - undefined if it is valid

removeSchema(name: string)

Remove a schema or the whole structure from the djv environment


resolve(name: string?)

Resolve the name by existing environment

// => { name: 'test', schema: {} }, fn: ... }

export(name: string?) -> state: object

Export the whole structure object from environment or resolved by a given name

// => { test: { name: 'test', schema: {}, ... } }

where state is an internal structure or only resolved schema object

import(config: object)

Import all found structure objects to internal environment structure


addFormat(name: string, formatter: string/function)

Add formatter to djv environment. When a string is passed it is interpreted as an expression which when returns true goes with an error, when returns false then a property is valid. When a function is passed it will be executed during schema compilation with a current schema and template helper arguments.

env.addFormat('UpperCase', '%s !== %s.toUpperCase()');
// or
env.addFormat('isOk', function(schema, tpl){
  return `!${schema.isOk}`;
env.validate('ok', 'valid') // => undefined if schema contains isOk property

setErrorHandler(errorHandler: function)

Specify custom error handler which will be used in generated functions when problem found. The function should return a string expression, which will be executed when generated validator function is executed. The simpliest use case is the default one @see template/defaultErrorHandler

 function defaultErrorHandler(errorType) {
   return `return "${errorType}: ${tpl.data}";`;

It returns an expression 'return ...', so the output is an error string.

djv({ errorHandler: () => 'return { error: true };' }) // => returns an object
  errorHandler(type) {
    return `errors.push({
      type: '${type}',
      schema: '${this.schema[this.schema.length - 1]}',
      data: '${this.data[this.data.length - 1]}'

When a custom error handler is used, the template body function adds a error variable inside a generated validator, which can be used to put error information. errorType is always passed to error handler function. Some validate utilities put extra argument, like f.e. currently processed property value. Inside the handler context is a templater instance, which contains this.schema, this.data paths arrays to identify validator position. @see test/index/setErrorHandler for more examples

useVersion(version: string, configure: function)

To customize environment provide a configure function which will update configuration for djv instance.

// or
env.useVersion('custom', configure)

Configure will get internal properties as an argument. Check the @korzio/djv-draft-04 code.

exposed = {

!Important Modifing them will affect all djv instances in an application.


npm test