jsonpolice

jsonpolice

A Javascript library implementing the JSON Schema specifications. Version 4 (draft) of the specification is supported by default, additional versions can be registered via the addVersion function.

The library decorates parsed objects in order to have them return default values defined the in the schema, for undefined properties.

Install

$ npm install jsonpolice

create(dataOrUri, store, retriever)

Create a new instance of schema validator. The schema itself is validated against the version of the specification the schema uses, as specified with the $schema property (defaults to http://json-schema.org/draft-04/schema#).

• dataOrUri, the schema to parse or a fully qualified URI to pass to retriever to download the schema
• store (optional), an object to use to cache resolved id and $ref values. If no store is passed, one is automatically created. Pass a store if you are going to parse several schemas or URIs referencing the same id and $ref values.
• retriever (optional), a function accepting a URL in input and returning a promise resolved to an object representing the data downloaded for the URI. Whenever a $ref to a new URI is found, if the URI is not already cached in the store in use, it'll be fetched using this retriever. If not retriever is passed and a URI needs to be downloaded, a no_retriever exception is thrown. Refer to the documentation of jsonref for sample retriever functions to use with the browser or with Node.js.

The function returns a Promise resolving to a new instance of Schema. Once created, a schema instance can be used repeatedly to validate data, calling the method Schema.validate.

Example

var jsonpolice = require('jsonpolice');

jsonpolice.create({
  type: 'object',
  properties: {
    d: {
      type: 'string',
      format: 'date-time'
    },
    i: {
      type: 'integer'
    },
    b: {
      type: [ 'boolean', 'number' ]
    },
    c: {
      default: 5
    }
  }
}).then(function(schema) {
  console.log(schema.validate({
    d: (new Date()).toISOString(),
    i: 6,
    b: true
  }));
});

addVersion(dataOrUri, retriever)

Register a new version of the specification that can be later used to validate schemas against. You can use this function to register custom extensions to the basic JSON Schema specification

• dataOrUri, the data to parse or a fully qualified URI to pass to retriever to download the data
• retriever (optional), a function accepting a URL in input and returning a promise resolved to an object representing the data downloaded for the URI. Whenever a $ref to a new URI is found, if the URI is not already cached in the store in use, it'll be fetched using this retriever. If not retriever is passed and a URI needs to be downloaded, a no_retriever exception is thrown.

The function returns a Promise resolving to the parsed data, with all $ref instances resolved.

Example

var jsonpolice = require('jsonpolice');

jsonpolice.addVersion({
  id: 'http://vivocha.com/sampleSwaggerParameter#',
  allOf: [
    { $ref: 'http://json-schema.org/draft-04/schema#' },
    {
      type: 'object',
      properties: {
        collectionFormat: {
          enum: [ 'csv', 'ssv', 'tsv', 'pipes' ],
          default: 'csv'
        }
      }
    }
  ]
}).then(function() {
  jsonpolice.create({
    $schema: 'http://vivocha.com/sampleSwaggerParameter#',
    type: 'object',
    properties: {
      a: {
        type: 'array',
        collectionFormat: 'ssv',
        items: {
          type: 'integer'
        }
      }
    }
  }).then(function(schema) {
    console.log(schema.validate({ a: "5 10 15" }));
  });
});

Schema.validate(data)

Validates the input data

• data, the data to parse

Returns a decorated version of data, that returns default values of undefined properties, according to the schema used to validate the data. Throws a ValidationError exception in case an error is encountered.

Additionally, type coercion is applied when possible and needed, as described in the following table:

Type	Format	Input type	Output type	Conversion
string	date-time	string	Date	output = new Date(input)
number		string	number	output = +input
boolean		string	boolean	true if "true" or "1", false if "false" or "0"
Array		string	Array	output = input.split(',')

For arrays, the library supports coercion from strings using by the default the comma-separated format (csv). Similarly to the OpenAPI specification (Swagger), it's possible to specify a different format using the collectionFormat property: the supported formats are csv, ssv, tsv and pipes.

Example

Using the following schema:

{
  type: 'object',
  properties: {
    d: {
      type: 'string',
      format: 'date-time'
    },
    i: {
      type: 'integer'
    },
    b: {
      type: [ 'boolean', 'number' ]
    },
    c: {
      default: 5
    }
  }
}

And parsing the following data:

var output = schema.validate({
  d: '2016-03-18T16:33:46.651Z',
  i: '10',
  b: '1',
  a: "5,7"
});

Produces the following output:

{
  "d": "2016-03-18T16:33:46.651Z",
  "i": 10,
  "b": true,
  "a": [
    5,
    7
  ]
}

output.c === 5; // true
result.d instanceof Date; // true