ajv-keywords

What is ajv-keywords?

The ajv-keywords package extends AJV (Another JSON Schema Validator) with additional keywords for JSON schema validation. It allows for more complex validation scenarios beyond what is available in the standard JSON Schema.

What are ajv-keywords's main functionalities?

dynamicDefaults

Allows setting dynamic defaults for properties, such as generating timestamps for createdAt fields.

{"properties": {"createdAt": {"type": "string", "format": "date-time", "default": "dynamic", "dynamicDefault": "datetime"}}}

transform

Enables transformation of data before validation. For example, trimming whitespace and converting text to lowercase.

{"properties": {"email": {"type": "string", "transform": ["trim", "toLowerCase"]}}}

range

Introduces exclusive range validation for numeric values, allowing for minimum and maximum values to be exclusive.

{"properties": {"age": {"type": "number", "exclusiveRange": true, "minimum": 18, "maximum": 60}}}

Other packages similar to ajv-keywords

jsonschema

A JSON Schema validator that supports draft-04/06/07. It's similar to ajv-keywords in providing JSON schema validation but does not offer the same level of keyword extension for custom validation scenarios.

tv4

Tiny Validator (tv4) is a lightweight JSON Schema validator that supports draft-04. While it provides basic validation capabilities, it lacks the extensibility and additional keywords provided by ajv-keywords.

README

ajv-keywords

Custom JSON-Schema keywords for ajv validator

Contents

• Install
• Usage
• Keywords
  • typeof
  • instanceof
  • range and exclusiveRange
  • propertyNames
  • regexp
  • dynamicDefaults
• License

Install

npm install ajv-keywords

Usage

To add all available keywords:

var Ajv = require('ajv');
var ajv = new Ajv;
require('ajv-keywords')(ajv);

ajv.validate({ instanceof: 'RegExp' }, /.*/); // true
ajv.validate({ instanceof: 'RegExp' }, '.*'); // false

To add a single keyword:

require('ajv-keywords')(ajv, 'instanceof');

To add multiple keywords:

require('ajv-keywords')(ajv, ['typeof', 'instanceof']);

To add a single keyword in browser (to avoid adding unused code):

require('ajv-keywords/keywords/instanceof')(ajv);

Keywords

typeof

Based on JavaScript typeof operation.

The value of the keyword should be a string ("undefined", "string", "number", "object", "function", "boolean" or "symbol") or array of strings.

To pass validation the result of typeof operation on the value should be equal to the string (or one of the strings in the array).

ajv.validate({ typeof: 'undefined' }, undefined); // true
ajv.validate({ typeof: 'undefined' }, null); // false
ajv.validate({ typeof: ['undefined', 'object'] }, null); // true

instanceof

Based on JavaScript typeof operation.

The value of the keyword should be a string ("Object", "Array", "Function", "Number", "String", "Date", "RegExp" or "Buffer") or array of strings.

To pass validation the result of data instanceof ... operation on the value should be true:

ajv.validate({ instanceof: 'Array' }, []); // true
ajv.validate({ instanceof: 'Array' }, {}); // false
ajv.validate({ instanceof: ['Array', 'Function'] }, funciton(){}); // true

You can add your own constructor function to be recognised by this keyword:

function MyClass() {}
var instanceofDefinition = require('ajv-keywords').get('instanceof').definition;
// or require('ajv-keywords/keywords/instanceof').definition;
instanceofDefinition.CONSTRUCTORS.MyClass = MyClass;

ajv.validate({ instanceof: 'MyClass' }, new MyClass); // true

range and exclusiveRange

Syntax sugar for the combination of minimum and maximum keywords, also fails schema compilation if there are no numbers in the range.

The value of this keyword must be the array consisting of two numbers, the second must be greater or equal than the first one.

If the validated value is not a number the validation passes, otherwise to pas validation the value should be greater (or equal) than the first number and smaller (or equal) than the second number in the array. If exclusiveRange keyword is present in the same schema and its value is true, the validated value must not be equal to the range boundaries.

var schema = { range: [1, 3] };
ajv.validate(schema, 1); // true
ajv.validate(schema, 2); // true
ajv.validate(schema, 3); // true
ajv.validate(schema, 0.99); // false
ajv.validate(schema, 3.01); // false

var schema = { range: [1, 3], exclusiveRange: true };
ajv.validate(schema, 1.01); // true
ajv.validate(schema, 2); // true
ajv.validate(schema, 2.99); // true
ajv.validate(schema, 1); // false
ajv.validate(schema, 3); // false

propertyNames

This keyword allows to define the schema for the property names of the object. The value of this keyword should be a valid JSON schema (v5 schemas are supported with Ajv option {v5: true}).

var schema = {
  type: 'object'
  propertyNames: {
    anyOf: [
      { format: ipv4 },
      { format: hostname }
    ]
  }
};

var validData = {
  '192.128.0.1': {},
  'test.example.com': {}
};

var invalidData = {
  '1.2.3': {}
};

ajv.validate(schema, validData); // true
ajv.validate(schema, invalidData); // false

regexp

This keyword allows to use regular expressions with flags in schemas (the standard pattern keyword does not support flags). The value of this keyword can be either a string (the result of regexp.toString()) or an object with the properties pattern and flags (the same strings that should be passed to RegExp constructor).

var schema = {
  type: 'object',
  properties: {
    foo: { regexp: '/foo/i' },
    bar: { regexp: { pattern: 'bar', flags: 'i' } }
  }
};

var validData = {
  foo: 'Food',
  bar: 'Barmen'
};

var invalidData = {
  foo: 'fog',
  bar: 'bad'
};

dynamicDefaults

This keyword allows to assign dynamic defaults to properties, such as timestamps, unique IDs etc.

This keyword only works if useDefaults options is used and not inside anyOf keywrods etc., in the same way as default keyword treated by Ajv.

The keyword should be added on the object level. Its value should be an object with each property corresponding to a property name, in the same way as in standard properties keyword. The value of each property can be:

• an identifier of default function (a string)
• an object with properties func (an identifier) and args (an object with parameters that will be passed to this function during schema compilation - see examples).

The properties used in dynamicDefaults should not be added to required keyword (or validation will fail), because unlike default this keyword is processed after validation.

There are several predefined dynamic default functions:

• "timestamp" - current timestamp in milliseconds
• "datetime"' - current date and time as string (ISO, valid according to date-time` format)
• "date"' - current date as string (ISO, valid according to date` format)
• "time" - current time as string (ISO, valid according to time format)
• "random" - pseudo-random number in [0, 1) interval
• "randomint" - pseudo-random integer number. If string is used as a property value, the function will randomly return 0 or 1. If object {func: 'randomint', max: N} is used then the default will be an integer number in [0, N) interval.
• "seq" - sequential integer number starting from 0. If string is used as a property value, the default sequence will be used. If object {func: 'seq', name: 'foo'} is used then the sequence with name "foo" will be used. Sequences are global, even if different ajv instances are used.

var schema = {
  type: 'object',
  dynamicDefaults: {
    ts: 'datetime',
    r: { func: 'randomint', max: 100 },
    id: { func: 'seq', name: 'id' }
  },
  properties: {
    ts: {
      type: 'string',
      format: 'datetime'
    },
    r: {
      type: 'integer',
      minimum: 0,
      maximum: 100,
      exclusiveMaximum: true
    },
    id: {
      type: 'integer',
      minimum: 0
    }
  }
};

var data = {};
ajv.validate(data); // true
data; // { ts: '2016-12-01T22:07:28.829Z', r: 25, id: 0 }

var data1 = {};
ajv.validate(data1); // true
data1; // { ts: '2016-12-01T22:07:29.832Z', r: 68, id: 1 }

ajv.validate(data1); // true
data1; // didn't change, as all properties were defined

You can add your own dynamic default function to be recognised by this keyword:

var uuid = require('uuid');

function uuidV4() { return uuid.v4(); }

var definition = require('ajv-keywords').get('dynamicDefaults').definition;
// or require('ajv-keywords/keywords/dynamicDefaults').definition;
definition.DEFAULTS.uuid = uuidV4;

var schema = {
  dynamicDefaults: { id: 'uuid' },
  properties: { id: { type: 'string', format: 'uuid' } }
};

var data = {};
ajv.validate(schema, data); // true
data; // { id: 'a1183fbe-697b-4030-9bcc-cfeb282a9150' };

var data1 = {};
ajv.validate(schema, data1); // true
data1; // { id: '5b008de7-1669-467a-a5c6-70fa244d7209' }

You also can define dynamic default that accepts parameters, e.g. version of uuid:

var uuid = require('uuid');

function getUuid(args) {
  var version = 'v' + (arvs && args.v || 4);
  return function() {
    return uuid[version]();
  };
}

var definition = require('ajv-keywords').get('dynamicDefaults').definition;
definition.DEFAULTS.uuid = getUuid;

var schema = {
  dynamicDefaults: {
    id1: 'uuid', // v4
    id2: { func: 'uuid', v: 4 }, // v4
    id3: { func: 'uuid', v: 1 } // v1
  }
};

License

MIT