validate-value validates values against JSON schemas. 

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validate-value

## [9.3.1](https://github.com/thenativeweb/validate-value/compare/9.3.0...9.3.1) (2022-03-24)

* Update dependencies. ([#421](https://github.com/thenativeweb/validate-value/issues/421)) ([a995239](https://github.com/thenativeweb/validate-value/commit/a9952393155831b7620bc9b588f31e68e7affe3a))

# [9.3.0](https://github.com/thenativeweb/validate-value/compare/9.2.2...9.3.0) (2022-03-21)

* Support custom Ajv instances ([#419](https://github.com/thenativeweb/validate-value/issues/419)) ([e4b602e](https://github.com/thenativeweb/validate-value/commit/e4b602e36fe1c071717857206dc98397657c003b))

## [9.2.2](https://github.com/thenativeweb/validate-value/compare/9.2.1...9.2.2) (2022-02-03)

* Add missing dependency @types/json-schema. ([#415](https://github.com/thenativeweb/validate-value/issues/415)) ([04e4c22](https://github.com/thenativeweb/validate-value/commit/04e4c220bff8bebf1d53065dc098a54f774577d8))

## [9.2.1](https://github.com/thenativeweb/validate-value/compare/9.2.0...9.2.1) (2022-02-01)

* Update dependencies assertthat and defekt. ([#414](https://github.com/thenativeweb/validate-value/issues/414)) ([bada9ec](https://github.com/thenativeweb/validate-value/commit/bada9ec9fe454fbe1431829245f6b19bfb4fb539))

# [9.2.0](https://github.com/thenativeweb/validate-value/compare/9.1.7...9.2.0) (2022-01-17)

* Improve readme. ([#405](https://github.com/thenativeweb/validate-value/issues/405)) ([98687b8](https://github.com/thenativeweb/validate-value/commit/98687b82c7b8210e8e8255dc2b170b7b306cf469))

## [9.1.7](https://github.com/thenativeweb/validate-value/compare/9.1.6...9.1.7) (2021-12-07)

* Remove non-existent function from documenation. ([#402](https://github.com/thenativeweb/validate-value/issues/402)) ([4bfb4e3](https://github.com/thenativeweb/validate-value/commit/4bfb4e3a4f6a623180645f9f8c56c82c46988052))

## [9.1.6](https://github.com/thenativeweb/validate-value/compare/9.1.5...9.1.6) (2021-08-16)

* bump typedescriptor from 4.0.11 to 4.0.12 ([#382](https://github.com/thenativeweb/validate-value/issues/382)) ([ebfccb3](https://github.com/thenativeweb/validate-value/commit/ebfccb3743a8a775202e390e7fddfcb7fbdf6bf5))

## [9.1.5](https://github.com/thenativeweb/validate-value/compare/9.1.4...9.1.5) (2021-08-16)

* bump ajv-formats from 2.1.0 to 2.1.1 ([#385](https://github.com/thenativeweb/validate-value/issues/385)) ([e09790a](https://github.com/thenativeweb/validate-value/commit/e09790a4aa0a72578a7c07447fa17170d903d062))

## [9.1.4](https://github.com/thenativeweb/validate-value/compare/9.1.3...9.1.4) (2021-08-02)

* bump typedescriptor from 4.0.10 to 4.0.11 ([#377](https://github.com/thenativeweb/validate-value/issues/377)) ([5585327](https://github.com/thenativeweb/validate-value/commit/558532798234430bb3873d5a9ad92ff423ac2719))

## [9.1.3](https://github.com/thenativeweb/validate-value/compare/9.1.2...9.1.3) (2021-07-23)

* Update dependencies. ([#376](https://github.com/thenativeweb/validate-value/issues/376)) ([be60c1a](https://github.com/thenativeweb/validate-value/commit/be60c1af2e5fc02350c495981a8be073c67c972d))

## [9.1.2](https://github.com/thenativeweb/validate-value/compare/9.1.1...9.1.2) (2021-07-21)

* bump typedescriptor from 4.0.9 to 4.0.10 ([#373](https://github.com/thenativeweb/validate-value/issues/373)) ([a656cd6](https://github.com/thenativeweb/validate-value/commit/a656cd64a4ee424a51eaa082baef9b1bbb2ce413))

## [9.1.1](https://github.com/thenativeweb/validate-value/compare/9.1.0...9.1.1) (2021-07-21)

* bump ajv from 8.6.1 to 8.6.2 ([#374](https://github.com/thenativeweb/validate-value/issues/374)) ([14dd0ff](https://github.com/thenativeweb/validate-value/commit/14dd0ffa1a8a7d005fd52d3ad5a39385933af84e))

# [9.1.0](https://github.com/thenativeweb/validate-value/compare/9.0.12...9.1.0) (2021-07-10)

* Bump multiple dependencies. ([#370](https://github.com/thenativeweb/validate-value/issues/370)) ([ac94554](https://github.com/thenativeweb/validate-value/commit/ac94554442eff44506c3ec8f03596c9e00aef4dd))

## [9.0.12](https://github.com/thenativeweb/validate-value/compare/9.0.11...9.0.12) (2021-07-06)

* bump ajv from 8.6.0 to 8.6.1 ([#369](https://github.com/thenativeweb/validate-value/issues/369)) ([64e79e4](https://github.com/thenativeweb/validate-value/commit/64e79e4dc05e7f1c09c849bf135cb087aee6b1c6))

## [9.0.11](https://github.com/thenativeweb/validate-value/compare/9.0.10...9.0.11) (2021-06-29)

* bump typedescriptor from 4.0.7 to 4.0.8 ([#365](https://github.com/thenativeweb/validate-value/issues/365)) ([fe9d508](https://github.com/thenativeweb/validate-value/commit/fe9d508417ffdc03eef2809b1434d95409725fb8))

## [9.0.10](https://github.com/thenativeweb/validate-value/compare/9.0.9...9.0.10) (2021-06-28)

  "description": "validate-value validates values against JSON schemas.",

      "email": "golo.roden@thenativeweb.io"

      "email": "jan-hendrik.grundhoefer@thenativeweb.io"

      "email": "hannes.leutloff@thenativeweb.io"

      "email": "alexander.kampf@thenativeweb.io"

      "email": "matthiashermsen@gmail.com"

    "semantic-release-configuration": "2.0.7"

    "url": "git://github.com/thenativeweb/validate-value.git"

| Category         | Status                                                                                                      |

| ---------------- | ----------------------------------------------------------------------------------------------------------- |

| Version          | [![npm](https://img.shields.io/npm/v/validate-value)](https://www.npmjs.com/package/validate-value)         |

| Build            | ![GitHub Actions](https://github.com/thenativeweb/validate-value/workflows/Release/badge.svg?branch=main)   |

| License          | ![GitHub](https://img.shields.io/github/license/thenativeweb/validate-value)                                |

The rewrite of `validate-value` in version 9.0.0 follows the infamous quote "parse, don't validate"<sup>[1](#footnote-1)</sup>. The quote asserts that parsing data is more valuable than validating it. This is very obvious when comparing the two approaches in TypeScript:

const doThingsWithValidation = async function (options: unknown): Promise<void> {

  // This throws, if the options are not valid.

  const typedOptions = options as Options;

  doSomethingWithAnOption(typedOptions.someOption);

const doThingsWithParsing = async function (options: unknown): Promise<Result<void, Error>> {

  // This parses the options and unwraps them, throwing if they were invalid.

  // If invalid options were something our program could handle, we would not

  // want to throw here and instead handle the error appropriately.

  // In this example we want the function to throw, if the options are invalid.

  const typedOptions = parseOptions(options).unwrapOrThrow();

In the second example, the `typedOptions` contained in the `Result` returned from the `parseOptions` call already have the type that we expect them to have and we don't have to assert them or assign them to a new variable in any way. This combines better support from the TypeScript compiler with better error handling from [`defekt`](https://github.com/thenativeweb/defekt/).

First you need to integrate validate-value into your application:

const { parse, Parser } = require('validate-value');

If you use TypeScript, use the following code instead:

import { parse, Parser } from 'validate-value';

Then, create a new instance and provide a [JSON schema](https://json-schema.org/learn/getting-started-step-by-step.html) that you would like to use for parsing:

If you are using TypeScript, you will want to provide a type for the parsed value:

Afterwards, you may use the `parse` function to parse a value:

    // The user object did not match the parser's schema. This should be handled.

    // The user object was parsed successfully and the result's value can now be used.

    doSomethingWithUser(parseResult.value);

  // The user object was parsed successfully and the result's value can now be used.

  doSomethingWithUser(parseResult.value);

After parsing, the value in the returned `Result` will have the type `User`, since it was passed to the parser upon construction.

For details on the error handling in the example above, check the [documentation of the `Result` type in `defekt`](https://github.com/thenativeweb/defekt#using-result).

If you want to, you can configure the parser according to your needs.

By default, the error message uses `value` as identifier and `.` as the separator for the object that is parsed, but sometimes you may want to change this. Therefore, provide the desired identifier and separator as second parameter to the `parse` function:

const parseResult = parser.parse(user, { valueName: 'person', separator: '/' });

Sometimes it is desired to use a custom validator instance, e.g. if you want to add custom formats. For that, you can hand over a custom [Ajv](https://ajv.js.org/) instance to the parser:

// Adjust Ajv instance according to your needs...

const parser = new Parser<User>(schema, {

Optionally, you can build upon the default instance that is used internally. For that, call the `getDefaultAjvInstance` function:

const ajvInstance = getDefaultAjvInstance();

For convenience, there is also the `parse` function, which skips the creation of a parser instance. You can use this if you're only going to use a schema for validation once. Otherwise, it is recommended to first create a parser instance, since then the JSON schema is only compiled once:

#### Verifying that a variable is of a specific type

To verify that a variable is of a specific type, use the `isOfType` function. Hand over the value you would like to verify, and a JSON schema describing that type. The function returns `true` if the given variable matches the schema, and `false` if it doesn't:

const { isOfType } = require('validate-value');

When using TypeScript, you may even specify a generic type parameter, and use the function as a type guard:

import { isOfType, JsonSchema } from 'validate-value';

		{
		"name": "validate-value",
		"version": "9.3.0",
		"version": "9.3.1",
		"description": "validate-value validates values against JSON schemas.",
		@@ -32,5 +32,5 @@ "contributors": [
		"@types/json-schema": "7.0.10",
		"ajv": "8.10.0",
		"ajv": "8.11.0",
		"ajv-formats": "2.1.1",
		"defekt": "8.2.0",
		"defekt": "9.1.0",
		"json-schema": "0.4.0",
		@@ -40,4 +40,4 @@ "typedescriptor": "4.0.12"
		"devDependencies": {
		"assertthat": "6.4.0",
		"roboter": "12.7.1",
		"assertthat": "6.5.1",
		"roboter": "13.0.0",
		"semantic-release-configuration": "2.0.7"
		@@ -44,0 +44,0 @@ },

Improved metrics

Dependency changes

		@@ -0,1 +1,8 @@
		## [9.3.1](https://github.com/thenativeweb/validate-value/compare/9.3.0...9.3.1) (2022-03-24)


		### Bug Fixes

		* Update dependencies. ([#421](https://github.com/thenativeweb/validate-value/issues/421)) ([a995239](https://github.com/thenativeweb/validate-value/commit/a9952393155831b7620bc9b588f31e68e7affe3a))

		# [9.3.0](https://github.com/thenativeweb/validate-value/compare/9.2.2...9.3.0) (2022-03-21)
		@@ -2,0 +9,0 @@

		@@ -104,6 +104,6 @@ # validate-value
		if (parseResult.hasError()) {
		// The user object did not match the parser's schema. This should be handled.
		// The user object did not match the parser's schema. This should be handled.
		} else {
		// The user object was parsed successfully and the result's value can now be used.
		doSomethingWithUser(parseResult.value);
		// The user object was parsed successfully and the result's value can now be used.
		doSomethingWithUser(parseResult.value);
		}
		@@ -110,0 +110,0 @@ ```