koa-ajv

Koa validator middleware based on ajv JSON-schema validator. You will need support for async/await so Node >=7.6 and Koa2 is the ideal combo.

Overview

The middleware allows you to define parameter validation rules for all of your routes and enforces them as defined in your JSON-schema like configuration. It leverages Ajvs superb performance qualities to efficiently validate route parameters against a compiled set of your custom validation rules.

You can install koa-ajv directly via NPM:

npm install koa-ajv

Examples

To validate parameters, you need to provide a JSON-schema definition for each route. A simple example:

const KoaAjv = require('koa-ajv');

const routes = {
  '/my/test/route/:param': {
    param: {
      type: 'string'
    }
  }
};

// Returns the validator middleware
KoaAjv({routes: routes});

You can use all directives supported by JSON-schema. To distinguish between request methods (defaults to GET), prefix your route validation definition with the request method:

{
  'POST /my/test/route': {
    param: {
      type: 'string',
      maxLength: 8
    }
  }
}

If the validation succeeds, filtered params are available in ctx.vparams and the request is passed downstream. Should the validation fail the middleware throws an error:

ctx.throw(400, 'validation error', ...);

The error object will contain validationErrors object with full details about the error. You should catch this error upstream and handle accordingly.

See some more examples

Configuration

The middleware accepts the following configuration options (default values here):

// Strict mode: require all routes to have their validation
// rules defined
strict: true,

// Log debug information
debug: false,

// Show extended error information. extended=false formats
// the errors into human-readable strings
extended: true,

// Routes config
routes: {},

// Additional config passed directly to 'ajv'
// See 'ajv' on NPM for further reference
validator: {

// Support v5 JSON schemas
  v5: true,

// Set to true to return all validation errors before failing
  allErrors: false,

// Parameters are coerced to their expected types
  coerceTypes: true,

// Omit all additional parameters not defined in route config
  removeAdditional: 'all',
}