jsvutil

A Node.js utility wrapper for the JSON Schema Validator (JSV).

Overview

JSV is an excellent module by Gary Court. This jsvutil module provides a simple framework around JSV for validating JSON instances and checking JSON schemas.

Features

This module augments JSV with the following features:

1. A validate function that combines JSV report errors into a single Error exception instance.
2. Applies any default values in the schema to the instance being validated.
3. A check function that validates a schema.
4. Supports callback functions as well as standard exceptions (useful in Node.js environments).

Installation

$ npm install jsvutil

Examples

The following two examples illustrate how a configuration file can be validated. Note that the validate function applies the default values in the schema so that after validation, the config object returned by the validate function may be different than the one read using the require function.

Using Exceptions

var jsvutil = require('jsvutil')
var config = require('./config.json');
var schema = require('./schema.json');

try {
    config = jsvutil.validate(config, schema);
    console.log('config file is valid');
} catch (e) {
    console.error(e.message);
    process.exit(1);
}

// Use the config object...

Using Callbacks

var jsvutil = require('jsvutil')
var config = require('./config.json');
var schema = require('./schema.json');

jsvutil.validate(config, schema, function (err, config) {
    if (err) {
        console.error(e.message);
        process.exit(1);
    } else {
        console.log('config file is valid');
    }
});

// Use the config object...

API

This section specifies the Application Programming Interface (API) for the jsvutil package. The API consists of the validate and check functions.

Important: If the instance or schema parameter is a string, then it is parsed as JSON text using the JSON.parse function. Otherwise, it must be a JSON-compatible JavaScript object or array. This is consistent with RFC 4627 and inconsistent with ECMAScript 5 § 15.12, which allows strings as top level productions.

The optional callback function complies with Node.js conventions. The first argument is either an error object on failure or null on success. The second argument is the equivalent return value of the function.

validate (function)

validate(instance, schema, [cb])

Validates the specified instance against the specified schema. The return value (or callback value) is the JSON instance with any schema default values applied to any unset instance values. The original instance parameter is not modified by this function.

Parameters:

• instance - {String|Object|Array} The JSON instance to validate. The instance is parsed using the JSON.parse function if it is a string.
• schema - {String|Object} The JSON schema against which to validate the instance. The schema is parsed using the JSON.parse function if it is a string.
• [cb] - {Function} The optional cb(err, instance) callback function.

Returns:

• {Object|Array} The validated JSON instance with any schema default values applied to any unset instance values.

Errors:

• Throws an error (or passes it to the callback function) if the specified JSON instance cannot be validated.

check (function)

check(schema, [cb])

Checks that the specified schema is valid.

Parameters:

• schema - {String|Object} The schema to check. The schema is parsed using the JSON.parse function if it is a string.
• [cb] - {Function} The optional cb(err, schema) callback function.

Returns:

• {Object} The JSON schema on success.

Errors:

• Throws an error (or passes it to the callback function) if the specified JSON schema is invalid.

License (MIT)

Copyright (c) 2012 Frank Hellwig

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.