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celebrate is an express middleware function that wraps the joi validation library. This allows you to use this middleware in any single route, or globally, and ensure that all of your inputs are correct before any handler function. The middleware allows you to validate req.params, req.headers, and req.query.

The middleware will also validate:

• req.body — provided you are using body-parser
• req.cookies — provided you are using cookie-parser
• req.signedCookies — provided you are using cookie-parser

celebrate lists joi as a formal dependency. This means that celebrate will always use a predictable, known version of joi during the validation and compilation steps. There are two reasons for this:

1. To ensure that celebrate can always use the latest version of joi as soon as it's published
2. So that celebrate can export the version of joi it uses to the consumer to maximize compatibility

Wondering why another joi middleware library for express? Full blog post here.

• express Compatibility
• Example Usage
• API
  • celebrate(schema, [joiOptions], [opts])
  • errors([opts])
  • Joi
  • Segments
  • CelebrateError(error, segment, [opts])
  • isCelebrate(err)
• Additional Details
  • Validation Order
  • Mutation Warning
  • Additional Info
• Issues

express Compatibility

celebrate is tested and has full compatibility with express 4 and 5. It likely works correctly with express 3, but including it in the test matrix was more trouble than it's worth. This is primarily because express 3 exposes route parameters as an array rather than an object.

Example Usage

Example of using celebrate on a single POST route to validate req.body.

const express = require('express');
const BodyParser = require('body-parser');
const { celebrate, Joi, errors, Segments } = require('celebrate');

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

app.post('/signup', celebrate({
  [Segments.BODY]: Joi.object().keys({
    name: Joi.string().required(),
    age: Joi.number().integer(),
    role: Joi.string().default('admin')
  }),
  [Segments.QUERY]: {
    token: Joi.string().token().required()
  }
}), (req, res) => {
  // At this point, req.body has been validated and 
  // req.body.role is equal to req.body.role if provided in the POST or set to 'admin' by joi
});
app.use(errors());

Example of using celebrate to validate all incoming requests to ensure the token header is present and matches the supplied regular expression.

const express = require('express');
const { celebrate, Joi, errors, Segments } = require('celebrate');
const app = express();

// validate all incoming request headers for the token header
// if missing or not the correct format, respond with an error
app.use(celebrate({
  [Segments.HEADERS]: Joi.object({
    token: Joi.string().required().regex(/abc\d{3}/)
  }).unknown()
}));
app.get('/', (req, res) => { res.send('hello world'); });
app.get('/foo', (req, res) => { res.send('a foo request'); });
app.use(errors());

API

celebrate does not have a default export. The following methods encompass the public API.

celebrate(schema, [joiOptions], [opts])

Returns a function with the middleware signature ((req, res, next)).

• requestRules - an object where key can be one of the values from Segments and the value is a joi validation schema. Only the keys specified will be validated against the incoming request object. If you omit a key, that part of the req object will not be validated. A schema must contain at least one valid key.
• [joiOpts] - optional object containing joi options that are passed directly into the validate function. Defaults to { warnings: true }.
• [opts] - an optional object with the following keys. Defaults to {}.
  • reqContext - bool value that instructs joi to use the incoming req object as the context value during joi validation. If set, this will trump the value of joiOptions.context. This is useful if you want to validate part of the request object against another part of the request object. See the tests for more details.

errors([opts])

Returns a function with the error handler signature ((err, req, res, next)). This should be placed with any other error handling middleware to catch celebrate errors. If the incoming err object is an error originating from celebrate, errors() will respond a pre-build error object. Otherwise, it will call next(err) and will pass the error along and will need to be processed by another error handler.

• [opts] - an optional object with the following keys
  • statusCode - number that will be used for the response status code in the event of an error. Must be greater than 399 and less than 600. It must also be a number available to the node HTTP module. Defaults to 400.

If the error response format does not suite your needs, you are encouraged to write your own and check isCelebrate(err) to format celebrate errors to your liking.

Errors origintating from the celebrate() middleware are CelebrateError objects.

Joi

celebrate exports the version of joi it is using internally. For maximum compatibility, you should use this version when creating schemas used with celebrate.

Segments

An enum containing all the segments of req objects that celebrate can valiate against.

{
  BODY: 'body',
  COOKIES: 'cookies',
  HEADERS: 'headers',
  PARAMS: 'params',
  QUERY: 'query',
  SIGNEDCOOKIES: 'signedCookies',
}

CelebrateError(error, segment, [opts])

A factory function for creating celebrate errors.

• err - a Joi validation error object
• segment - A Segment indicating the step where the validation failed.
• [opts] - optional object with the following keys
  • celebrated - bool that, when true, adds Symbol('celebrated'): true to the result object. This indicates this error as originating from celebrate. You'd likely want to set this to true if you want the celebrate error handler to handle errors originating from the format function that you call in user-land code. Defaults to false.

Sample usage

  const result = Joi.validate(req.params.id, Joi.string().valid('foo'), { abortEarly: false });
  const err = CelebrateError(result.error, Segments.PARAMS);

isCelebrate(err)

Returns true if the provided err object originated from the celebrate middleware, and false otherwise. Useful if you want to write your own error handler for celebrate errors.

• err - an error object

Additional Details

Validation Order

celebrate validates request values in the following order:

1. req.headers
2. req.params
3. req.query
4. req.cookies (assuming cookie-parser is being used)
5. req.signedCookies (assuming cookie-parser is being used)
6. req.body (assuming body-parser is being used)

If any of the configured validation rules fail, the entire request will be considered invalid and the rest of the validation will be short-circuited and the validation error will be passed into next.

Mutation Warning

If you use any of joi's updating validation APIs (default, rename, etc.) celebrate will override the source value with the changes applied by joi.

For example, if you validate req.query and have a default value in your joi schema, if the incoming req.query is missing a value for default, during validation celebrate will overrite the original req.query with the result of joi.validate. This is done so that once req has been validated, you can be sure all the inputs are valid and ready to consume in your handler functions and you don't need to re-write all your handlers to look for the query values in res.locals.*.

Additional Info

According the the HTTP spec, GET requests should not include a body in the request payload. For that reason, celebrate does not validate the body on GET requests.

Issues

Before opening issues on this repo, make sure your joi schema is correct and working as you intended. The bulk of this code is just exposing the joi API as express middleware. All of the heavy lifting still happens inside joi. You can go here to verify your joi schema easily.