ajv-keywords/README.md

# ajv-keywords

Custom JSON-Schema keywords for [Ajv](https://github.com/epoberezkin/ajv) validator

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**Please note**: This readme file is for [ajv-keywords v5.0.0](https://github.com/ajv-validator/ajv-keywords/releases/tag/v5.0.0) that should be used with [ajv v8](https://github.com/ajv-validator/ajv).

[ajv-keywords v3](https://github.com/ajv-validator/ajv-keywords/tree/v3) should be used with [ajv v6](https://github.com/ajv-validator/ajv/tree/v6).

## Contents

- [Install](#install)
- [Usage](#usage)
- [Keywords](#keywords)
  - [Types](#types)
    - [typeof](#typeof)
    - [instanceof](#instanceof)<sup>\+</sup>
  - [Keywords for numbers](#keywords-for-numbers)
    - [range and exclusiveRange](#range-and-exclusiverange)
  - [Keywords for strings](#keywords-for-strings)
    - [regexp](#regexp)
    - [transform](#transform)<sup>\*</sup>
  - [Keywords for arrays](#keywords-for-arrays)
    - [uniqueItemProperties](#uniqueitemproperties)<sup>\+</sup>
  - [Keywords for objects](#keywords-for-objects)
    - [allRequired](#allrequired)
    - [anyRequired](#anyrequired)
    - [oneRequired](#onerequired)
    - [patternRequired](#patternrequired)
    - [prohibited](#prohibited)
    - [deepProperties](#deepproperties)
    - [deepRequired](#deeprequired)
    - [dynamicDefaults](#dynamicdefaults)<sup>\*</sup><sup>\+</sup>
  - [Keywords for all types](#keywords-for-all-types)
    - [select/selectCases/selectDefault](#selectselectcasesselectdefault)
- [Security contact](#security-contact)
- [Open-source software support](#open-source-software-support)
- [License](#license)

<sup>\*</sup> - keywords that modify data
<sup>\+</sup> - keywords that are not supported in [standalone validation code](https://github.com/ajv-validator/ajv/blob/master/docs/standalone.md)

## Install

To install version 4 to use with [Ajv v7](https://github.com/ajv-validator/ajv):

```
npm install ajv-keywords
```

## Usage

To add all available keywords:

```javascript
const Ajv = require("ajv")
const ajv = new Ajv()
require("ajv-keywords")(ajv)

ajv.validate({instanceof: "RegExp"}, /.*/) // true
ajv.validate({instanceof: "RegExp"}, ".*") // false
```

To add a single keyword:

```javascript
require("ajv-keywords")(ajv, "instanceof")
```

To add multiple keywords:

```javascript
require("ajv-keywords")(ajv, ["typeof", "instanceof"])
```

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

```javascript
require("ajv-keywords/dist/keywords/select")(ajv, opts)
```

To add all keywords via Ajv options:

```javascript
const ajv = new Ajv({keywords: require("ajv-keywords/dist/definitions")(opts)})
```

To add one or several keywords via options:

```javascript
const ajv = new Ajv({
  keywords: [
    require("ajv-keywords/dist/definitions/typeof")(),
    require("ajv-keywords/dist/definitions/instanceof")(),
    // select exports an array of 3 definitions - see "select" in docs
    ...require("ajv-keywords/dist/definitions/select")(opts),
  ],
})
```

`opts` is an optional object with a property `defaultMeta` - URI of meta-schema to use for keywords that use subschemas (`select` and `deepProperties`). The default is `"http://json-schema.org/schema"`.

## 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 an 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).

```javascript
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"` or `"Promise"`) or an array of strings.

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

```javascript
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:

```javascript
class MyClass {}
const instanceofDef = require("ajv-keywords/dist/definitions/instanceof")
instanceofDef.CONSTRUCTORS.MyClass = MyClass
ajv.validate({instanceof: "MyClass"}, new MyClass()) // true
```

**Please note**: currently `instanceof` is not supported in [standalone validation code](https://github.com/ajv-validator/ajv/blob/master/docs/standalone.md) - it has to be implemented as [`code` keyword](https://github.com/ajv-validator/ajv/blob/master/docs/keywords.md#define-keyword-with-code-generation-function) to support it (PR is welcome).

### Keywords for numbers

#### `range` and `exclusiveRange`

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

The value of these keywords must be an 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.

```javascript
const schema = {type: "number", 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

const schema = {type: "number", exclusiveRange: [1, 3]}
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, and also without `"u"` flag when needed (the standard `pattern` keyword does not support flags and implies the presence of `"u"` flag).

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).

```javascript
const schema = {
  type: "object",
  properties: {
    foo: {type: "string", regexp: "/foo/i"},
    bar: {type: "string", regexp: {pattern: "bar", flags: "i"}},
  },
}

const validData = {
  foo: "Food",
  bar: "Barmen",
}

const invalidData = {
  foo: "fog",
  bar: "bad",
}
```

#### `transform`

This keyword allows a string to be modified during validation.

This keyword applies only to strings. If the data is not a string, the `transform` keyword is ignored.

A standalone string cannot be modified, i.e. `data = 'a'; ajv.validate(schema, data);`, because strings are passed by value

**Supported transformations:**

- `trim`: remove whitespace from start and end
- `trimStart`/`trimLeft`: remove whitespace from start
- `trimEnd`/`trimRight`: remove whitespace from end
- `toLowerCase`: convert to lower case
- `toUpperCase`: convert to upper case
- `toEnumCase`: change string case to be equal to one of `enum` values in the schema

Transformations are applied in the order they are listed.

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

**Example: multiple transformations**

```javascript
require("ajv-keywords")(ajv, "transform")

const schema = {
  type: "array",
  items: {
    type: "string",
    transform: ["trim", "toLowerCase"],
  },
}

const data = ["  MixCase  "]
ajv.validate(schema, data)
console.log(data) // ['mixcase']
```

**Example: `enumcase`**

```javascript
require("ajv-keywords")(ajv, ["transform"])

const schema = {
  type: "array",
  items: {
    type: "string",
    transform: ["trim", "toEnumCase"],
    enum: ["pH"],
  },
}

const 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.

```javascript
const schema = {
  type: "array",
  uniqueItemProperties: ["id", "name"],
}

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

const invalidData1 = [
  {id: 1},
  {id: 1}, // duplicate "id"
  {id: 3},
]

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

This keyword is contributed by [@blainesch](https://github.com/blainesch).

**Please note**: currently `uniqueItemProperties` is not supported in [standalone validation code](https://github.com/ajv-validator/ajv/blob/master/docs/standalone.md) - it has to be implemented as [`code` keyword](https://github.com/ajv-validator/ajv/blob/master/docs/keywords.md#define-keyword-with-code-generation-function) to support it (PR is welcome).

### Keywords for objects

#### `allRequired`

This keyword allows to require the presence of all properties used in `properties` keyword in the same schema object.

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

The value of this keyword must be boolean.

If the value of the keyword is `false`, the validation succeeds.

If the value of the keyword is `true`, the validation succeeds if the data contains all properties defined in `properties` keyword (in the same schema object).

If the `properties` keyword is not present in the same schema object, schema compilation will throw exception.

```javascript
const schema = {
  type: "object",
  properties: {
    foo: {type: 'number'},
    bar: {type: 'number'}
  }
  allRequired: true
};

const validData = { foo: 1, bar: 2 };
const alsoValidData = { foo: 1, bar: 2, baz: 3 };

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

#### `anyRequired`

This keyword allows to require the presence of any (at least one) property from the list.

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

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

```javascript
const schema = {
  type: "object",
  anyRequired: ["foo", "bar"],
}

const validData = {foo: 1}
const alsoValidData = {foo: 1, bar: 2}

const invalidDataList = [{}, {baz: 3}]
```

#### `oneRequired`

This keyword allows to require the presence of only one property from the list.

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

The value of this keyword must be an array of strings, each string being a property name. For data object to be valid exactly one of the properties in this array should be present in the object.

```javascript
const schema = {
  type: "object",
  oneRequired: ["foo", "bar"],
}

const validData = {foo: 1}
const alsoValidData = {bar: 2, baz: 3}

const invalidDataList = [{}, {baz: 3}, {foo: 1, bar: 2}]
```

#### `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.

```javascript
const schema = {
  type: "object",
  patternRequired: ["f.*o", "b.*r"],
}

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

const 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.

```javascript
const schema = {
  type: "object",
  prohibited: ["foo", "bar"],
}

const validData = {baz: 1}
const alsoValidData = {}

const invalidDataList = [{foo: 1}, {bar: 2}, {foo: 1, bar: 2}]
```

**Please note**: `{prohibited: ['foo', 'bar']}` is equivalent to `{not: {anyRequired: ['foo', 'bar']}}` (i.e. it has the same validation result for any data).

#### `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.

```javascript
const schema = {
  type: "object",
  deepProperties: {
    "/users/1/role": {enum: ["admin"]},
  },
}

const validData = {
  users: [
    {},
    {
      id: 123,
      role: "admin",
    },
  ],
}

const alsoValidData = {
  users: {
    1: {
      id: 123,
      role: "admin",
    },
  },
}

const invalidData = {
  users: [
    {},
    {
      id: 123,
      role: "user",
    },
  ],
}

const 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.

```javascript
const schema = {
  type: "object",
  deepRequired: ["/users/1/role"],
}

const validData = {
  users: [
    {},
    {
      id: 123,
      role: "admin",
    },
  ],
}

const invalidData = {
  users: [
    {},
    {
      id: 123,
    },
  ],
}
```

See [json-schema-org/json-schema-spec#203](https://github.com/json-schema-org/json-schema-spec/issues/203#issue-197211916) for an example of the equivalent schema without `deepRequired` keyword.

### Keywords for all types

#### `select`/`selectCases`/`selectDefault`

**Please note**: these keywords are deprecated. It is recommended to use OpenAPI [discriminator](https://ajv.js.org/json-schema.html#discriminator) keyword supported by Ajv v8 instead of `select`.

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](https://github.com/ajv-validator/ajv/blob/master/docs/validation.md#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 (also 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.

This keyword correctly tracks evaluated properties and items to work with `unevaluatedProperties` and `unevaluatedItems` keywords - only properties and items from the subschema that was used (one of `selectCases` subschemas or `selectDefault` subschema) are marked as evaluated.

**Please note**: these keywords require Ajv `$data` option to support [\$data reference](https://github.com/ajv-validator/ajv/blob/master/docs/validation.md#data-reference).

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

const 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'] }
    }
  }
};

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

const invalidDataList = [
  { kind: 'foo' }, // no property foo
  { kind: 'bar' }, // no property 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
];
```

#### `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](https://github.com/epoberezkin/ajv#assigning-defaults).

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 dynamic 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 in the same schema (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.

```javascript
const 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,
    },
  },
}

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

const 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 `allOf` [compound keyword](https://github.com/epoberezkin/ajv/blob/master/KEYWORDS.md#compound-keywords) to execute `dynamicDefaults` before validation.

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

const 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:

```javascript
const uuid = require("uuid")

const def = require("ajv-keywords/dist/definitions/dynamicDefaults")
def.DEFAULTS.uuid = () => uuid.v4

const schema = {
  dynamicDefaults: {id: "uuid"},
  properties: {id: {type: "string", format: "uuid"}},
}

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

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

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

```javascript
const uuid = require("uuid")

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

const def = require("ajv-keywords/dist/definitions/dynamicDefaults")
def.DEFAULTS.uuid = getUuid

const schema = {
  dynamicDefaults: {
    id1: "uuid", // v4
    id2: {func: "uuid", v: 4}, // v4
    id3: {func: "uuid", v: 1}, // v1
  },
}
```

**Please note**: dynamic default functions are differentiated by the number of parameters they have (`function.length`). Functions that do not expect default must have one non-optional argument so that `function.length` > 0.

`dynamicDefaults` is not supported in [standalone validation code](https://github.com/ajv-validator/ajv/blob/master/docs/standalone.md).

## Security contact

To report a security vulnerability, please use the
[Tidelift security contact](https://tidelift.com/security).
Tidelift will coordinate the fix and disclosure.

Please do NOT report security vulnerabilities via GitHub issues.

## Open-source software support

Ajv-keywords is a part of [Tidelift subscription](https://tidelift.com/subscription/pkg/npm-ajv-keywords?utm_source=npm-ajv-keywords&utm_medium=referral&utm_campaign=readme) - it provides a centralised support to open-source software users, in addition to the support provided by software maintainers.

## License

[MIT](https://github.com/epoberezkin/ajv-keywords/blob/master/LICENSE)