2.17.3 • Public • Published


Temporary fork from is-my-json-valid to have my fixes in

A JSONSchema validator that uses code generation to be extremely fast

npm install is-my-json-valid

It passes the entire JSONSchema v4 test suite except for remoteRefs and maxLength/minLength when using unicode surrogate pairs.

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Simply pass a schema to compile it

var validator = require('is-my-json-valid')

var validate = validator({
  required: true,
  type: 'object',
  properties: {
    hello: {
      required: true,
      type: 'string'

console.log('should be valid', validate({hello: 'world'}))
console.log('should not be valid', validate({}))

// get the last list of errors by checking validate.errors
// the following will print [{field: 'data.hello', message: 'is required'}]

You can also pass the schema as a string

var validate = validator('{"type": ... }')

Optionally you can use the require submodule to load a schema from __dirname

var validator = require('is-my-json-valid/require')
var validate = validator('my-schema.json')

Custom formats

is-my-json-valid supports the formats specified in JSON schema v4 (such as date-time). If you want to add your own custom formats pass them as the formats options to the validator

var validate = validator({
  type: 'string',
  required: true,
  format: 'only-a'
}, {
  formats: {
    'only-a': /^a+$/

console.log(validate('aa')) // true
console.log(validate('ab')) // false

External schemas

You can pass in external schemas that you reference using the $ref attribute as the schemas option

var ext = {
  required: true,
  type: 'string'

var schema = {
  $ref: '#ext' // references another schema called ext

// pass the external schemas as an option
var validate = validator(schema, {schemas: {ext: ext}})

validate('hello') // returns true
validate(42) // return false

Filtering away additional properties

is-my-json-valid supports filtering away properties not in the schema

var filter = validator.filter({
  required: true,
  type: 'object',
  properties: {
    hello: {type: 'string', required: true}
  additionalProperties: false

var doc = {hello: 'world', notInSchema: true}
console.log(filter(doc)) // {hello: 'world'}

Verbose mode shows more information about the source of the error

When the verbose options is set to true, is-my-json-valid also outputs:

  • value: The data value that caused the error
  • schemaPath: an array of keys indicating which sub-schema failed
var schema = {
  required: true,
  type: 'object',
  properties: {
    hello: {
      required: true,
      type: 'string'
var validate = validator(schema, {
  verbose: true

validate({hello: 100});
// [ { field: 'data.hello',
//     message: 'is the wrong type',
//     value: 100,
//     type: 'string',
//     schemaPath: [ 'properties', 'hello' ] } ]

Many popular libraries make it easy to retrieve the failing rule with the schemaPath:

var schemaPath = validate.errors[0].schemaPath
var R = require('ramda')

console.log( 'All evaluate to the same thing: ', R.equals(
  { required: true, type: 'string' },
  R.path(schemaPath, schema),
  require('lodash').get(schema, schemaPath),
  require('jsonpointer').get(schema, [""].concat(schemaPath))
// All evaluate to the same thing: true

Greedy mode tries to validate as much as possible

By default is-my-json-valid bails on first validation error but when greedy is set to true it tries to validate as much as possible:

var validate = validator({
  type: 'object',
  properties: {
    x: {
      type: 'number'
  required: ['x', 'y']
}, {
  greedy: true

validate({x: 'string'});
console.log(validate.errors) // [{field: 'data.y', message: 'is required'},
                             //  {field: 'data.x', message: 'is the wrong type'}]

Error messages

Here is a list of possible message values for errors:

  • is required
  • is the wrong type
  • has additional items
  • must be FORMAT format (FORMAT is the format property from the schema)
  • must be unique
  • must be an enum value
  • dependencies not set
  • has additional properties
  • referenced schema does not match
  • negative schema matches
  • pattern mismatch
  • no schemas match
  • no (or more than one) schemas match
  • has a remainder
  • has more properties than allowed
  • has less properties than allowed
  • has more items than allowed
  • has less items than allowed
  • has longer length than allowed
  • has less length than allowed
  • is less than minimum
  • is more than maximum


is-my-json-valid uses code generation to turn your JSON schema into basic javascript code that is easily optimizeable by v8.

At the time of writing, is-my-json-valid is the fastest validator when running

If you know any other relevant benchmarks open a PR and I'll add them.



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