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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:

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
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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)).

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

This is a curried version of celebrate. It is curried with lodash.curryRight so it can be called in all the various fashions that API supports. Returns a function with the middleware signature ((req, res, next)).

<details> <summary>Sample usage</summary>

This is an example use of curried celebrate in a real server.

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

  // now every instance of `celebrate` will use these same options so you only
  // need to do it once.
  const celebrate = celebrator({ reqContext: true }, { convert: true });

  // 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('/', celebrate({
    [Segments.HEADERS]: Joi.object({
      name: Joi.string().required()
    })
  }), (req, res) => { res.send('hello world'); });
  app.use(errors());

Here are some examples of other ways to call celebrator

  const opts = { reqContext: true };
  const joiOpts = { convert: true };
  const schema = {
    [Segments.HEADERS]: Joi.object({
      name: Joi.string().required()
    })
  };

  let c = celebrator(opts)(joiOpts)(schema);
  c = celebrator(opts, joiOpts)(schema);
  c = celebrator(opts)(joiOpts, schema);
  c = celebrator(opts, joiOpts, schema);

  // c would function the same in all of these cases.
</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.

If the error response format does not suite your needs, you are encouraged to write your own and check isCelebrateError(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 validate against.

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

Modes

An enum containing all the available validation modes that celebrate can support.

new CelebrateError([message], [opts])

Creates a new CelebrateError object. Extends the built in Error object.

CelebrateError has the following public properties:

<details> <summary>Sample usage</summary> 
  const result = Joi.validate(req.params.id, Joi.string().valid('foo'), { abortEarly: false });
  const err = new CelebrateError(undefined, { celebrated: true });
  err.details.set(Segments.PARAMS, result.error);
</details>

isCelebrateError(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.

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)

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 (assuming the request is valid).

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 overwrite 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.