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
  • Types
    • typeof
    • instanceof
  • Keywords for numbers
    • range and exclusiveRange
  • Keywords for strings
    • regexp
    • formatMaximum / formatMinimum and formatExclusiveMaximum / formatExclusiveMinimum
    • transform^*
  • Keywords for arrays
    • uniqueItemProperties
  • Keywords for objects
    • patternRequired
    • prohibited
    • deepProperties
    • deepRequired
  • Compound keywords
    • switch
    • select/selectCases/selectDefault (BETA)
  • Keywords for all types
    • dynamicDefaults^*
• License

^* - keywords that modify data

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

Types

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 instanceof operation.

The value of the keyword should be a string ("Object", "Array", "Function", "Number", "String", "Date", "RegExp", "Promise" 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'] }, function(){}); // 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

Keywords for numbers

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 pass 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

Keywords for strings

regexp

This keyword allows to use regular expressions with flags in schemas (the standard pattern keyword does not support flags).

This keyword applies only to strings. If the data is not a string, the validation succeeds.

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'
};

formatMaximum / formatMinimum and formatExclusiveMaximum / formatExclusiveMinimum

These keywords allow to define minimum/maximum constraints when the format keyword defines ordering.

These keywords apply only to strings. If the data is not a string, the validation succeeds.

The value of keyword formatMaximum (formatMinimum) should be a string. This value is the maximum (minimum) allowed value for the data to be valid as determined by format keyword.

When this keyword is added, it defines comparison rules for formats "date", "time" and "date-time". Custom formats also can have comparison rules. See addFormat method.

The value of keyword formatExclusiveMaximum (formatExclusiveMinimum) should be a boolean value. These keyword cannot be used without formatMaximum (formatMinimum). If this keyword value is equal to true, the data to be valid should not be equal to the value in formatMaximum (formatMinimum) keyword.

require('ajv-keywords')(ajv, ['formatMinimum', 'formatMaximum']);

var schema = {
  format: 'date',
  formatMinimum: '2016-02-06',
  formatMaximum: '2016-12-27',
  formatExclusiveMaximum: true
}

var validDataList = ['2016-02-06', '2016-12-26', 1];

var invalidDataList = ['2016-02-05', '2016-12-27', 'abc'];

transform

This keyword allows a string to be modified before validation.

These keywords apply only to strings. If the data is not a string, the transform is skipped.

There are limitation due to how ajv is written:

• a stand alone string cannot be transformed. ie data = 'a'; ajv.validate(schema, data);
• currently cannot work with ajv-pack

Supported options:

• trim: remove whitespace from start and end
• trimLeft: remove whitespace from start
• trimRight: remove whitespace from end
• toLowerCase: case string to all lower case
• toUpperCase: case string to all upper case
• toEnumCase: case string to match case in schema

Options are applied in the order they are listed.

Note: toEnumCase requires that all allowed values are unique when case insensitive.

Example: multiple options

require('ajv-keywords')(ajv, ['transform']);

var schema = {
  type: 'array',
  items: {
    type:'string',
    transform:['trim','toLowerCase']
  }
};

var data = ['  MixCase  '];
ajv.validate(schema, data);
console.log(data); // ['mixcase']

Example: enumcase

require('ajv-keywords')(ajv, ['transform']);

var schema = {
  type: 'array',
  items: {
    type:'string',
    transform:['trim','toEnumCase'],
    enum:['pH']
  }
};

var data = ['ph',' Ph','PH','pH '];
ajv.validate(schema, data);
console.log(data); // ['pH','pH','pH','pH']

Keywords for arrays

uniqueItemProperties

The keyword allows to check that some properties in array items are unique.

This keyword applies only to arrays. If the data is not an array, the validation succeeds.

The value of this keyword must be an array of strings - property names that should have unique values across all items.

var schema = { uniqueItemProperties: [ "id", "name" ] };

var validData = [
  { id: 1 },
  { id: 2 },
  { id: 3 }
];

var invalidData1 = [
  { id: 1 },
  { id: 1 },
  { id: 3 }
];

var invalidData2 = [
  { id: 1, name: "taco" },
  { id: 2, name: "taco" }, // duplicate "name"
  { id: 3, name: "salsa" }
];

This keyword is contributed by @blainesch.

Keywords for objects

patternRequired

This keyword allows to require the presence of properties that match some pattern(s).

This keyword applies only to objects. If the data is not an object, the validation succeeds.

The value of this keyword should be an array of strings, each string being a regular expression. For data object to be valid each regular expression in this array should match at least one property name in the data object.

If the array contains multiple regular expressions, more than one expression can match the same property name.

var schema = { patternRequired: [ 'f.*o', 'b.*r' ] };

var validData = { foo: 1, bar: 2 };
var alsoValidData = { foobar: 3 };

var invalidDataList = [ {}, { foo: 1 }, { bar: 2 } ];

prohibited

This keyword allows to prohibit that any of the properties in the list is present in the object.

This keyword applies only to objects. If the data is not an object, the validation succeeds.

The value of this keyword should be an array of strings, each string being a property name. For data object to be valid none of the properties in this array should be present in the object.

var schema = { prohibited: ['foo', 'bar']};

var validData = { baz: 1 };
var alsoValidData = {};

var invalidDataList = [
  { foo: 1 },
  { bar: 2 },
  { foo: 1, bar: 2}
];

deepProperties

This keyword allows to validate deep properties (identified by JSON pointers).

This keyword applies only to objects. If the data is not an object, the validation succeeds.

The value should be an object, where keys are JSON pointers to the data, starting from the current position in data, and the values are JSON schemas. For data object to be valid the value of each JSON pointer should be valid according to the corresponding schema.

var schema = {
  type: 'object',
  deepProperties: {
    "/users/1/role": { "enum": ["admin"] }
  }
};

var validData = {
  users: [
    {},
    {
      id: 123,
      role: 'admin'
    }
  ]
};

var alsoValidData = {
  users: {
    "1": {
      id: 123,
      role: 'admin'
    }
  }
};

var invalidData = {
  users: [
    {},
    {
      id: 123,
      role: 'user'
    }
  ]
};

var alsoInvalidData = {
  users: {
    "1": {
      id: 123,
      role: 'user'
    }
  }
};

deepRequired

This keyword allows to check that some deep properties (identified by JSON pointers) are available.

This keyword applies only to objects. If the data is not an object, the validation succeeds.

The value should be an array of JSON pointers to the data, starting from the current position in data. For data object to be valid each JSON pointer should be some existing part of the data.

var schema = {
  type: 'object',
  deepRequired: ["/users/1/role"]
};

var validData = {
  users: [
    {},
    {
      id: 123,
      role: 'admin'
    }
  ]
};

var invalidData = {
  users: [
    {},
    {
      id: 123
    }
  ]
};

See json-schema-org/json-schema-spec#203 for an example of the equivalent schema without deepRequired keyword.

Compound keywords

switch

This keyword allows to perform advanced conditional validation.

The value of the keyword is the array of if/then clauses. Each clause is the object with the following properties:

• if (optional) - the value is JSON-schema
• then (required) - the value is JSON-schema or boolean
• continue (optional) - the value is boolean

The validation process is dynamic; all clauses are executed sequentially in the following way:

1. if:
   1. if property is JSON-schema according to which the data is:
      1. valid => go to step 2.
      2. invalid => go to the NEXT clause, if this was the last clause the validation of switch SUCCEEDS.
   2. if property is absent => go to step 2.
2. then:
   1. then property is true or it is JSON-schema according to which the data is valid => go to step 3.
   2. then property is false or it is JSON-schema according to which the data is invalid => the validation of switch FAILS.
3. continue:
   1. continue property is true => go to the NEXT clause, if this was the last clause the validation of switch SUCCEEDS.
   2. continue property is false or absent => validation of switch SUCCEEDS.

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

var schema = {
  type: 'array',
  items: {
    type: 'integer',
    'switch': [
      { if: { not: { minimum: 1 } }, then: false },
      { if: { maximum: 10 }, then: true },
      { if: { maximum: 100 }, then: { multipleOf: 10 } },
      { if: { maximum: 1000 }, then: { multipleOf: 100 } },
      { then: false }
    ]
  }
};

var validItems = [1, 5, 10, 20, 50, 100, 200, 500, 1000];

var invalidItems = [1, 0, 2000, 11, 57, 123, 'foo'];

Please note: this keyword is moved here from Ajv, mainly to preserve backward compatibility. It is unlikely to become a standard. It's preferable to use if/then/else keywords if possible, as they are likely to be added to the standard. The above schema is equivalent to (for example):

{
  type: 'array',
  items: {
    type: 'integer',
    if: { minimum: 1, maximum: 10 },
    then: true,
    else: {
      if: { maximum: 100 },
      then: { multipleOf: 10 },
      else: {
        if: { maximum: 1000 },
        then: { multipleOf: 100 },
        else: false
      }
    }
  }
}

select/selectCases/selectDefault

These keywords allow to choose the schema to validate the data based on the value of some property in the validated data.

These keywords must be present in the same schema object (selectDefault is optional).

The value of select keyword should be a $data reference that points to any primitive JSON type (string, number, boolean or null) in the data that is validated. You can also use a constant of primitive type as the value of this keyword (e.g., for debugging purposes).

The value of selectCases keyword must be an object where each property name is a possible string representation of the value of select keyword and each property value is a corresponding schema (from draft-06 it can be boolean) that must be used to validate the data.

The value of selectDefault keyword is a schema (from draft-06 it can be boolean) that must be used to validate the data in case selectCases has no key equal to the stringified value of select keyword.

The validation succeeds in one of the following cases:

• the validation of data using selected schema succeeds,
• none of the schemas is selected for validation,
• the value of select is undefined (no property in the data that the data reference points to).

If select value (in data) is not a primitive type the validation fails.

Please note: these keywords require Ajv $data option to support $data reference.

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

var schema = {
  type: object,
  required: ['kind'],
  properties: {
    kind: { type: 'string' }
  },
  select: { $data: '0/kind' },
  selectCases: {
    foo: {
      required: ['foo'],
      properties: {
        kind: {},
        foo: { type: 'string' }
      },
      additionalProperties: false
    },
    bar: {
      required: ['bar'],
      properties: {
        kind: {},
        bar: { type: 'number' }
      },
      additionalProperties: false
    }
  },
  selectDefault: {
    propertyNames: {
      not: { enum: ['foo', 'bar'] }
    }
  }
};

var validDataList = [
  { kind: 'foo', foo: 'any' },
  { kind: 'bar', bar: 1 },
  { kind: 'anything_else', not_bar_or_foo: 'any value' }
];

var invalidDataList = [
  { kind: 'foo' }, // no propery foo
  { kind: 'bar' }, // no propery bar
  { kind: 'foo', foo: 'any', another: 'any value' }, // additional property
  { kind: 'bar', bar: 1, another: 'any value' }, // additional property
  { kind: 'anything_else', foo: 'any' } // property foo not allowed
  { kind: 'anything_else', bar: 1 } // property bar not allowed
];

Please note: the current implementation is BETA. It does not allow using relative URIs in $ref keywords in schemas in selectCases and selectDefault that point outside of these schemas. The workaround is to use absolute URIs (that can point to any (sub-)schema added to Ajv, including those inside the current root schema where select is used). See tests.

Keywords for all types

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 keywords 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', args: { 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', args: { 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', args: { max: 100 } },
    id: { func: 'seq', args: { name: 'id' } }
  },
  properties: {
    ts: {
      type: 'string',
      format: 'date-time'
    },
    r: {
      type: 'integer',
      minimum: 0,
      exclusiveMaximum: 100
    },
    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

When using the useDefaults option value "empty", properties and items equal to null or "" (empty string) will be considered missing and assigned defaults. Use the allOf compound keyword to execute dynamicDefaults before validation.

var schema = {
  allOf: [
    {
      dynamicDefaults: {
        ts: 'datetime',
        r: { func: 'randomint', args: { min: 5, max: 100 } },
        id: { func: 'seq', args: { name: 'id' } }
      }
    },
    {
      type: 'object',
      properties: {
        ts: {
          type: 'string'
        },
        r: {
          type: 'number',
          minimum: 5,
          exclusiveMaximum: 100
        },
        id: {
          type: 'integer',
          minimum: 0
        }
      }
    }
  ]
};

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

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