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.

    build status


    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.




    npm i @bahmutov/is-my-json-valid

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