JSON Schema Validator

A basic JSON Schema Validator

DISCLAIMER: This is a basic JSON Schema validator implementation, it dont implement the full JSON Schema spec, so it's should never used in production. For a faster and powerful JSON Schema validator, please use AJV

Install

npm install --save jsonschemav

Usage

const JsonSchemav = require('jsonschemav')
const jsv = new JsonSchemav()

const schema = {
  type: 'object',
  properties: {
    title: { type: 'string', minLength: 6 },
    date: { type: 'string', format: 'date', default: 'now()' }
  }
}
const data = { title: 'Hello, World!' }
const validator = jsv.compile(schema)

validator
  .then((instance) => instance.validate(datta))
  .then((parsedData) => {
    // use `parsedData` instead `data`
    console.log(parsedData)
    // { title: 'Hello, World!',
    //   date: '2017-06-12T18:49:14.739Z' }
  })

validator
  .then((instance) => instance.validate('Hello'))
  .catch((err) => {
    console.error(err.errors)
    // [ { keyword: 'minLength',
    //    size: 5,
    //    minLength: 6,
    //    message: 'not enough characters. must be greater than, or equal to, 6' } ]
  })

validator
  .then((instance) => instance.validate(true))
  .catch((err) => {
    console.error(err.errors)
    // [ { keyword: 'type', message: 'invalid type input' } ]
  })

Async Validation

const axios = require('axios')
const JsonSchemav = require('jsonschemav')

const jsv = new JsonSchemav()
const schema = { type: 'string', isTwitterAccount: true }
const endpoint = 'https://twitter.com/users/username_available'
const validationFn = (value, data) => {
  // value is the keyword value
  // data.value is the user data

  if (value === true) {
    return axios.get(`${endpoint}?username=${data.value}`)
      .then((response) => {
        if (response.data.valid) {
          const message = `The username '${data.value}' does not exists`
          const err = new Error()

          err.props = { message }

          throw err
        }

        return Promise.resolve(data.value)
      })
  }

  return true
}

jsv.addKeyword('string', 'isTwitterAccount', validationFn)

const validator = jsv.compile(schema)

validator
  .then((instance) => instance.validate('nonexistingac'))
  .catch((err) => {
    console.error(err.errors)
    // [ { message: 'The username \'nonexistingac\' does not exists',
    //     keyword: 'isTwitterAccount' } ]

  })

validator
  .then((instance) => instance.validate('demsking'))
  .then((parsedData) => {
    console.log('success')
  })

JSV API

Table of Contents

• validateSchema()
• compile()
• addCompileStep()
• addAlias()
• addType()
• removeType()
• addKeyword()
• removeKeyword()

validateSchema()

Validate a schema. Throws an error for invalid schema

Parameters

• schema object Schema to validate

Examples

const jsv = new JsonSchemav()
const schema = { type: 'string' }

try {
  jsv.validateSchema(schema)
} catch (err) {
  console.error(err)
}

compile()

Compile a schema

Parameters

• schema object Schema to compile

Examples

const jsv = new JsonSchemav()
const schema = {
  type: 'object',
  properties: {
    title: { type: 'string' },
    date: { type: 'string', format: 'date', default: 'now()' }
  }
}
const data = { title: 'Hello, World!' }

jsv.compile(schema)
  .then((instance) => instance.validate(data))
  .then((parsedData) => {
     // use `parsedData` instead `data`
     console.log(parsedData)
     // { title: 'Hello, World!',
     //   date: '2017-06-12T18:49:14.739Z' }
  })
  .catch((err) => {
     console.error(err.errors) // a list of parsing error
  })

Returns Promise Returns the validation interface on success and an error otherwise

addCompileStep()

Add a compile step function to a type

Parameters

• type string The name of the type
• compileStepFn function A compile function

addAlias()

Add an alias for a type

Parameters

• type string The name of a defined type
• name string The alias name

Examples

const jsv = new JsonSchemav()
const schema = { type: 'int' }
const data = 123

jsv.addAlias('integer', 'int')
jsv.compile(schema)
  .then((instance) => instance.validate(data))
  .then((parsedData) => {
     // use `parsedData` instead `data`
     console.log(parsedData) // 123
  })
  .catch((err) => {
     // err.errors is a list of parsing error
  })

addType()

Add a new type to the instance

Parameters

• name string The name of the new type
• validateFn function? A validate function for the new type

Examples

const jsv = new JsonSchemav()
const validateFn = (data) => {
  return Number.isInteger(data.value) && /^[01]+$/.test(data.value.toString())
}

jsv.addType('binary', validateFn)

const schema = { type: 'binary' }
const data = 1111011
const instance = jsv.compile(schema)

jsv.compile(schema)
  .then((instance) => instance.validate(data))
  .then((parsedData) => {
    // use `parsedData` instead `data`
    console.log(parsedData) // 1111011
  })

removeType()

Remove a type from the instance

Parameters

• name string The nema of the type

Examples

const schema = { type: 'string' }
const jsv = new JsonSchemav()

jsv.removeType('string')

try {
  jsv.validateSchema(schema)
} catch (err) {
  console.error(err) // Error: Unknown type 'string'
}

addKeyword()

Add a new keyword to a type

Parameters

• type string The name of the type
• name string The name of the new keyword
• validateFn function A validate function for the new keyword

Examples

const jsv = new JsonSchemav()
const validateFn = function (value, data) {
  // value is the keyword value
  // data.value is the user data
  // the function must returns:
  //   - true: for a success validation
  //   - false: for a faillure validate
  //   - an object { message, errors }
  //   - a Promise for async validation

  return new Promise((resolve, reject) => {
    //...
  })
}

jsv.addKeyword('string', 'provider', validateFn)

// and then
const schema = {
  type: 'object',
  properties: {
    account: { type: 'string', provider: 'twitter' }
  }
}

removeKeyword()

Remove a keyword from a type

Parameters

• type string The name of the type
• name string The name of the keyword

Examples

const jsv = new JsonSchemav()

jsv.removeKeyword('string', 'minLength')

const schema = { type: 'string', minLength: 5 }
const instance = jsv.compile(schema)
const data = 'abc'

jsv.compile(schema)
  .then((instance) => instance.validate(data))
  .then((parsedData) => {
     // success
  })

License

Under the MIT license. See LICENSE file for more details.