@valbo/validation-middlewares

Express middlewares to validate JSON request bodies.

Install

npm install @valbo/validation-middlewares

Usage

This package exports functions to validate data against JSON Schemas using Ajv.

validateSchema<SchemaId extends string>(ajv: Ajv, schemaId: SchemaId, data: unknown): void

Validates some data against a JSON Schema loaded in an Ajv instance. The function is generic, so you can specify which schema ids are valid. It will throw a 400 BadRequestError if the data is invalid.

createParseJsonBodyMiddleware(options?: OptionsJson): RequestHandler

A wrapper around the body-parser json() function. It returns a middleware that checks if the request has a Content-Type: application/json header and then parses the request body as a JSON.

The middleware throws a 415 Unsupported Media Type error if the header is missing, and a 400 Bad Request Error if it cannot parse the body.

configureValidateMiddleware<SchemaId extends string>(ajv: Ajv): (schemaId: Schema) => RequestHandler

It receives an Ajv instance configured with all the required JSON schemas and returns a function that receives the id of the JSON schema to use for validation. That returned function then returns a middleware that validates the request body against the provided schema.

The middleware throws a 400 Bad Request Error if the validation fails.

Example

import express from 'express';
import Ajv from 'ajv';
import { createParseJsonBodyMiddleware, configureValidateMiddleware, CreateValidateMiddleware } from '@valbo/validation-middlewares';

const parseBody = createParseBody({ limit: '1Mb' });

const findUserSchema = {
  type: 'object',
  properties: { username: { type: 'string' } },
  required: ['username'],
  additionalProperties: false,
};

const ajv = new Ajv();
ajv.addSchema(schema, 'findUserRequest')

type SchemaIds = 'findUserRequest';

const validateMiddleware: CreateValidateMiddleware<SchemaIds> = configureValidateMiddleware<SchemasIds>(ajv);

const app = express()
  .use(parseBody)
  .use('/users/find', validateMiddleware('findUserRequest'));