JJV: Javascript JSON Validator

A simple and extensible Javascript json-schema validator. Runs in the browser and in the server (through node.js), it has no dependencies and out-of-the-box AMD support.

See json-schema.org for examples and detailed documentation on the specification of JSON-schema. JJV supports the latest (v4) JSON Schema Core draft, but due to performance and security concerns remote schemas are not fetched.

Basic Usage

In the most basic usage an environment must be created, and one or more named schemas are registered in the environment. Javascript objects can then be validated against any registered schema.

// create new JJV environment
var env = jjv();

// Register a `user` schema
env.addSchema('user', {
    type: 'object',
    properties: {
        firstname: {
            type: 'string',
            minLength: 2
            maxLength: 15
        },
        lastname: {
            type: 'string',
            minLength: 2
            maxLength: 25
        },
        gender: {
            type: 'string',
            enum: ['male', 'female']
        },
        email: {
            type: 'string',
            format: 'email'
        },
        password: {
            type: 'string',
            minLength: 8
        }
    },
    required: ['firstname', 'lastname', 'email', 'password']
});

// Perform validation against an incomplete user object (errors will be reported)
var errors = env.validate('user', {firstname: 'John', lastname: 'Smith'});

// validation was successful
if (!errors) {
    alert('User has been validated.')
} else {
    alert('Failed with error object ' + JSON.stringify(errors));
}

Advanced Usage

There is built-in support for types string, boolean, number, integer, object, array and date. The types date and integer are custom JJV extensions not part of the JSON-Schema specification. JJV provides mechanisms to add support for custom types, custom formats, and custom checks.

Custom Types

Support for additional types can be added through the addType function. For example, a simple implementation of the date type (very close to the internal implementation) would be the following:

env.addType('date', function (v) {
  var d = new Date(v);
  if (isNaN(d.getTime()))
      throw new Error('is not a date');
  return d;
});

Custom Formats

It is also possible to add support for additional string formats through the addFormat function. For example, the internal implementation of the hexadecimal string format could be implemented as follows:

env.addFormat('hexadecimal', function (v) {
    if (typeof v !== 'string' || !(/^[a-fA-F0-9]+$/.test(v)))
        throw new Error('is not hexadecimal');
});

Custom Checks

Finally, it is possible to add support for custom checks (i.e., minItems, maxItems, minLength, maxLength, etc.) through the addCheck function. For example, the internal implementation of the minLength check could be implemented as follows:

env.addCheck('minLength', function (v) {
    if (v.length < p)
        throw new Error('too small');
});