express-validation is an express middleware that validates a request and returns a response with errors; if any of the configured validation rules fail.

We use joi to define validation rules. We have a hard dependency on Joi in order to avoid compatibility issues with Joi releases. We are using snyk, which should help with this process.

Currently support Joi v17.x.x

We support validating the following parameter types:

• headers
• params (path)
• query
• cookies
• signedCookies
• body

Install with npm:

npm i express-validation --save

Install with yarn:

yarn add express-validation

In order to setup and use express-validation consider the following simple express application. It has a single route; configured to use the express-validation middleware function validate; it accepts as input loginValidation; which defines validation rules for this route.

const express = require('express')
const bodyParser = require('body-parser')
const { validate, ValidationError, Joi } = require('express-validation')

const loginValidation = {
  body: Joi.object({
    email: Joi.string()
      .email()
      .required(),
    password: Joi.string()
      .regex(/[a-zA-Z0-9]{3,30}/)
      .required(),
  }),
}

const app = express();
app.use(bodyParser.json())

app.post('/login', validate(loginValidation, {}, {}), (req, res) => {
  res.json(200)
})

app.use(function(err, req, res, next) {
  if (err instanceof ValidationError) {
    return res.status(err.statusCode).json(err)
  }

  return res.status(500).json(err)
})

app.listen(3000)

We have defined two rules email and password. They are encapsulated inside body; which is important; as this defines their location within the request.

We also need to setup an express global error handler, express-validation will pass errors to this handler. We can check within the handler for errors of type validationError distinguishing validation errors from other types of error.

express-validation, by default will return errors in the following format, an object details keyed by parameter, each containing an array of errors in joi format.

{
      "name": "ValidationError",
      "message": "Validation Failed",
      "statusCode": 400,
      "error": "Bad Request",
      "details": {
        "body": [
          {
            "message": "\"password\" is not allowed to be empty",
            "path": [
              "password"
            ],
            "type": "string.empty",
            "context": {
              "label": "password",
              "value": "",
              "key": "password"
            }
          }
        ]
      }
    }

We support other simpler formats via configuration

• keyByField, flattens the error details object to a list of messages, keyed by field name

{
  "name": "ValidationError",
  "message": "Validation Failed",
  "statusCode": 400,
  "error": "Bad Request",
  "details": [
    { "accesstoken": "\"accesstoken\" is not allowed to be empty" },
    { "password": "\"password\" is not allowed to be empty" }
  ]
}

express-validation exposes the following api:

The exported validate function takes a schema object and two optional arguments, options and joiOptions and returns a validationError instance if schema contains errors.

Default: {}

Includes validition rules, defined using joi, the rules are keyed by the following parameter types:

• headers
• params (path)
• query
• cookies
• signedCookies
• body

Default: { context: false, statusCode: 400, keyByField: false }

Options, used by express-validation:

• context, grants Joi access to the request object. This allows you to:
  • reference other parts of the request in your validations, see Joi.ref
  • specify default values, see Joi.default
  • will also cast values, e.g. strings to integer
  • default { context: false }
• statusCode, defaults to 400, this will also set the error message via nodes status codes
  • default { statusCode: 400 }
• keyByField, flattens the error details object to a list of messages, keyed by field name

Default: {}

Options, used by joi, see Joi options, note:

We expose a custom error; ValidationError, use this in you global express error handler to distinguish validation errors from other types of error.

We also expose the version of Joi we have as a dependency, in order to avoid compatibility issues with other versions of Joi.

For more information on how to use express-validation please see the following examples:

abortEarly.test.js

You can return multiple errors, not just the first encountered, by setting, the joi option abortEarly: false

context.test.js

Enabling the context in options, allows you to reference other parts of the request in your validation.

default.test.js

You can specify joi default values in your schema.

This work is licensed under the MIT License (see the LICENSE file).

https://github.com/AndrewKeig/express-validation/blob/master/LICENSE