freeman-check

freeman-check

Simple type and format checking of JavaScript objects. This is a very popular utility at Freeman Industries.

Installation

npm install freeman-check --save

Usage

You can use freeman-check to validate JavaScript objects against a specified JSON schema.

In this example, the Check class is used to validate an object against a defined schema. If the object doesn't conform to the schema, a CheckError is thrown with details about the validation failure.

TypeScript example

import { Check, Schema, CheckError } from 'freeman-check';

const object = {
	name: "Nabil Freeman",
	email: "[e-mail]",
	favourite_films: [
		"Face/Off",
		"Bad Lieutenant",
		"The Wicker Man"
	]
};

const schema: Schema = {
	type: "object",
	properties: {
		name: {
			type: "string"
		},
		email: {
			type: "string",
			format: "email"
		},
		favourite_films: {
			type: "array",
			items: {
				type: "string"
			}
		}
	},
	required: ["name", "email", "favourite_films"]
};

const check = new Check(schema);

try {
	check.test(object);
	console.log("Object is valid!");
} catch (error: unknown) {
	if (error instanceof CheckError) {
		console.log(error.message);
		console.log(error.schema);
	}

	throw error;
}

JavaScript example

const { Check, CheckError } = require('freeman-check');

const object = {
	name: "Nabil Freeman",
	email: "[e-mail]",
	favourite_films: [
		"Face/Off",
		"Bad Lieutenant",
		"The Wicker Man"
	]
};

const schema = {
	type: "object",
	properties: {
		name: {
			type: "string"
		},
		email: {
			type: "string",
			format: "email"
		},
		favourite_films: {
			type: "array",
			items: {
				type: "string"
			}
		}
	},
	required: ["name", "email", "favourite_films"]
};

const check = new Check(schema);

try {
	check.test(object);
	console.log("Object is valid!");
} catch (error) {
	if (error instanceof CheckError) {
		console.log(error.message);
		console.log(error.schema);
	}

	throw error;
}

The Schema type

This type is directly exported from the jsonschema package for your convenience.

This is the library that the Check class uses to validate objects.

You can find more information about this library here:

https://www.npmjs.com/package/jsonschema

Compatibility with Schema types from other libraries

There are small inconsistencies between JSON Schema types from different libraries, because the standard is so flexible.

Depending on reported use cases it might be necessary to add support for a custom schema type.

If you think this applies to you, feel free to open an issue.