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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, req.query and req.body (provided you are using body-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.

⚠️Mutation Warning⚠️ If you use any of joi's updating validation APIs (defualt, 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.*.

express Compatibility

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

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 } = require('celebrate');

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

app.post('/signup', celebrate({
  body: Joi.object().keys({
    name: Joi.string().required(),
    age: Joi.number().integer(),
    role: Joi.string().default('admin')
  }),
  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 } = 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({
 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(schema, [options])

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

• schema - a object where key can be one of 'params', 'headers', 'query', and 'body' 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 of the valid keys.
• [options] - joi options that are passed directly into the validate function. Defaults to { escapeHtml: true }.

errors()

Returns a function with the error handler signature ((err, req, res, next)). This should be placed with any other error handling middleware to catch joi validation errors. If the incoming err object is an error originating from celebrate, errors() will respond with a 400 status code and the joi validation message. 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 format does not suite your needs, you are encouraged to write your own error handler and check isCelebrate(err) to format celebrate errors to your liking. The full joi error object will be available in your own error handler.

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.

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

Order

celebrate validates req values in the following order:

1. req.headers
2. req.params
3. req.query
4. req.body

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.

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.