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https://github.com/bahmutov/validate-by-example

Derives a JSON schema from an object and then uses it to validate other objects
https://github.com/bahmutov/validate-by-example

derive json json-schema train validate

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Derives a JSON schema from an object and then uses it to validate other objects

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# validate-by-example



> Derives a JSON schema from an object and then uses it to validate other objects



[![NPM][npm-icon] ][npm-url]



[![Build status][ci-image] ][ci-url]

[![semantic-release][semantic-image] ][semantic-url]

[![js-standard-style][standard-image]][standard-url]



## Goal



Derive [json schema][json-schema] from one object and use it to verify every

object after that. Uses [generate-schema][generate-schema] and

[is-my-json-valid][is-my-json-valid].



[json-schema]: http://json-schema.org/

[generate-schema]: https://github.com/nijikokun/generate-schema

[is-my-json-valid]: https://github.com/mafintosh/is-my-json-valid



## How to use



Install with `npm install --save validate-by-example`



In your code first train on an object (gives you a schema) and then validate

an object.



```js

const {train, validate} = require('validate-by-example')

const aPerson = {

  name: 'gleb',

  age: 37,

  married: true,

  lives: {

    city: 'Boston'

  }

}

const schema = train(person)

// now use schema to validate

const someone = {

  name: 'stranger',

  age: 'twenty',

  additional: 'some new property',

  lives: {

    state: 'MA'

  }

}

const result = validate(schema, someone)

// result is an object

// if everything goes well result.valid will be true

// otherwise

if (!result.valid) {

  console.log(result.errors)

}

```



The above example prints a few errors, because every property is required,

and no additional properties is allowed.



```json

[

  {

    "field": "data",

    "message": "has additional properties"

  },

  {

    "field": "data.age",

    "message": "is the wrong type"

  },

  {

    "field": "data.married",

    "message": "is required"

  },

  {

    "field": "data.lives",

    "message": "has additional properties"

  },

  {

    "field": "data.lives.city",

    "message": "is required"

  }

]

```



For error format, see

[is-my-json-valid](https://github.com/mafintosh/is-my-json-valid#error-messages)



See more in [tests](src/validate-by-example-spec.js)



## Inferring formats



For the top level properties, the `train` function tries to infer

specific [JSON schema v4 format][formats]. For example



```js

const {train} = require('validate-by-example')

const schema = train({created: '2017-02-16T15:30:28.370Z'})

/*

  {

    '$schema': 'http://json-schema.org/draft-04/schema#',

    type: 'object',

    properties: {

      created: {

        type: 'string', required: true, format: 'date-time'

      }

    },

    additionalProperties: false

  }

*/

```



**Note** only hex RGB strings like `#ff0ff` or `#FF00FF` are inferred as

`color` format.



## Overriding formats



You can specify [JSON schema v4 format][formats] for each property.



```js

const {train, validate} = require('validate-by-example')

const user = {

  email: '[email protected]'

}

const schema = train(user, {email: 'email'})

/*

  schema.properties.email will be

  {type: 'string', required: true, format: 'email'}

*/

validate({email: 'unknown'})

```



This is equivalent to



```js

const user = {

  email: '[email protected]'

}

const schema = train(user)

schema.properties.email.format = 'email'

validate(schema, {email: 'unknown'})

```



and will produce the following error



```json

{

  "valid": false,

  "errors": [

    {

      "field": "data.email",

      "message": "must be email format"

    }

  ]

}

```



[formats]: http://json-schema.org/latest/json-schema-validation.html#rfc.section.7.3



## JSON schema



Related projects that can derive JSON schema from an object



* [json-schema-by-example](https://github.com/japsu/json-schema-by-example)

* [json-schema-trainer](https://github.com/davisml/json-schema-trainer)



### Small print



Author: Gleb Bahmutov <[email protected]> © 2017



* [@bahmutov](https://twitter.com/bahmutov)

* [glebbahmutov.com](http://glebbahmutov.com)

* [blog](http://glebbahmutov.com/blog)



License: MIT - do anything with the code, but don't blame me if it does not work.



Support: if you find any problems with this module, email / tweet /

[open issue](https://github.com/bahmutov/validate-by-example/issues) on Github



## MIT License



Copyright (c) 2017 Gleb Bahmutov <[email protected]>



Permission is hereby granted, free of charge, to any person

obtaining a copy of this software and associated documentation

files (the "Software"), to deal in the Software without

restriction, including without limitation the rights to use,

copy, modify, merge, publish, distribute, sublicense, and/or sell

copies of the Software, and to permit persons to whom the

Software is furnished to do so, subject to the following

conditions:



The above copyright notice and this permission notice shall be

included in all copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

OTHER DEALINGS IN THE SOFTWARE.



[npm-icon]: https://nodei.co/npm/validate-by-example.svg?downloads=true

[npm-url]: https://npmjs.org/package/validate-by-example

[ci-image]: https://travis-ci.org/bahmutov/validate-by-example.svg?branch=master

[ci-url]: https://travis-ci.org/bahmutov/validate-by-example

[semantic-image]: https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg

[semantic-url]: https://github.com/semantic-release/semantic-release

[standard-image]: https://img.shields.io/badge/code%20style-standard-brightgreen.svg

[standard-url]: http://standardjs.com/