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express-validation

express-validation is a middleware that validates the body, params, query, headers and cookies of a request and returns a response with errors; if any of the configured validation rules fail.

express-validation

express-validation is a middleware that validates the body, params, query, headers and cookies of a request and returns a response with errors; if any of the configured validation rules fail.

$ npm install express-validation --save

express-validation supports validating the following:

  • body
  • params
  • query
  • headers
  • cookies

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; it accepts as input validation.login; which are the validation rules we have defined for this route.

file: test/app.js

var express = require('express')
  , validate = require('express-validation')
  , http = require('http')
  , bodyParser = require('body-parser')
  , cookieParser = require('cookie-parser')
  , app = express();
 
app.use(bodyParser.json())
app.use(cookieParser())
 
app.set('port', 3000);
 
app.post('/login', validate(validation.login), function(req, res){
    res.json(200);
});
 
// error handler, required as of 0.3.0 
app.use(function(err, req, res, next){
  res.status(400).json(err);
});
 
http.createServer(app);

The following section defines our validation rules validation.login. This is simply an object, which uses https://github.com/spumko/joi to define validation rules for a request.

We have defined two rules email and password. They are encapsulated inside body; which is important; as this defines their location, alternatives being, params, query, headers and cookies.

file: test/validation/login.js

var Joi = require('joi');
 
module.exports = {
  body: {
    email: Joi.string().email().required(),
    password: Joi.string().regex(/[a-zA-Z0-9]{3,30}/).required()
  }
};

The following test, calls the route defined in our express application /login; it passes in a payload with an email and empty password.

file: test/body.js

describe('when the request has a missing item in payload', function () {
  it('should return a 400 ok response and a single error', function(done){
 
    var login = {
        email: "andrew.keig@gmail.com",
        password: ""
    };
 
    request(app)
      .post('/login')
      .send(login)
      .expect(400)
      .end(function (err, res) {
        var response = JSON.parse(res.text);
        response.errors.length.should.equal(1);
        response.errors[0].messages.length.should.equal(2);
        done();
      });
    });
});

Running the above test will produce the following response.

{
  "status": 400,
  "statusText": "Bad Request",
  "errors": [
    {
      "field": "password",
      "location": "body",
      "messages": [
        "the value of password is not allowed to be empty",
        "the value of password must match the regular expression /[a-zA-Z0-9]{3,30}/"
      ],
      "types": [ "any.empty", "string.regex.base" ]
    }
  ]
}

Full code for these examples is to be found in test/ directory.

When Joi validates the body, params, query, headers or cookies it returns it as Javascript Object.

Example without express-validation:

app.post('/login', function(req, res){
  console.log(req.body); // => '{ "email": "user@domain", "password": "pwd" }'
  res.json(200);
});

Example with express-validation:

var validate = require('express-validation');
var validation = require('./test/validation/login.js');
 
app.post('/login', validate(validation.login), function(req, res){
  console.log(req.body); // => { email: "user@domain", password: "pwd" }
  res.json(200);
});

The difference might seem very slight, but it's a big deal. All parts of a request will be either parsed, or throw errors.

Enabling a configurable flag, contextRequest, the Joi validation can access parts of the node http.ClientRequest. This allows you to reference other parts of the request in your validations, as follows:

Example: Validate that the ID in the request params is the same ID as in the body for the endpoint /context/:id.

file: test/validation/context.js

var Joi = require('joi');
 
module.exports = {
  body: {
      id: Joi.string().valid(Joi.ref('$params.id')).required()
  }
};

The following test calls the /context/1 route in the express application; It passes a payload with the an id of '2'.

file: test/context.js

  describe('when the schema contains an invalid reference to the request object', function() {
    it('should return a 400 response', function(done) {
      request(app)
        .post('/context/1')
        .send({id: '2'})
        .expect(400)
        .end(function(err, res) {
          if(err) {
            return done(err);
          }
          done();
        });
    });
  });
});

Running the above test will produce the following response:

{
  "status": 400,
  "statusText": "Bad Request",
  "errors": [
    {
      "field": "id",
      "location": "body",
      "messages": [
        "\"id\" must be one of [context:params.id]"
      ],
      "types": [
        "any.allowOnly"
      ]
    }
  ]
}

When creating a validation object that checks req.headers; please remember to use lowercase names; node.js will convert incoming headers to lowercase:

var Joi = require('joi');
 
module.exports = {
  headers: {
    accesstoken: Joi.string().required(),
    userid : Joi.string().required()
  }
};

Since 0.4.0 express-validation calls next() with a ValidationError, a specific type of Error. This can be very handy when writing more complex error handlers for your Express application, a brief example follows:

var ev = require('express-validation');
 
// error handler 
app.use(function (err, req, res, next) {
  // specific for validation errors 
  if (err instanceof ev.ValidationError) return res.status(err.status).json(err);
 
  // other type of errors, it *might* also be a Runtime Error 
  // example handling 
  if (process.env.NODE_ENV !== 'production') {
    return res.status(500).send(err.stack);
  } else {
    return res.status(500);
  }
});

By default, additional fields outside of the schema definition will be ignored by validation.
To enforce strict checking, set the allowUnknown\* options as follows:

module.exports.post = {
  options : {
    allowUnknownBody: true,
    allowUnknownHeaders: true,
    allowUnknownQuery: true,
    allowUnknownParams: true,
    allowUnknownCookies: true
  },
  ...
};

With strict checking enabled, if additional fields gets sent through validation, they will be raise a ValidationError.

By default, the status code is set to 400, and status text to Bad Request, you can change this behaviour with the following:

module.exports.post = {
  options: {
    status: 422,
    statusText: 'Unprocessable Entity'
  },
  ...
};

Status code and text can also be customized globally. At the same time specific behaviour still applies.

var ev = require('express-validation');
// assign options 
ev.options({
  status: 422,
  statusText: 'Unprocessable Entity'
});
 
// clear options back to default 
ev.options();

Thanks to node require() caching, all the other express-validation instances also have the same set of global options.

Recap of all options usable both as global or per-validation basis.

allowUnknownBody: boolean - default: true
allowUnknownHeaders: boolean - default: true
allowUnknownQuery: boolean - default: true
allowUnknownParams: boolean - default: true
allowUnknownCookies: boolean - default: true
status: integer - default: 400
statusText: string - default: 'Bad Request'
contextRequest: boolean - default: false

1.0.0:

  • Removed flatten documentation as the functionality was broken since 0.5.0 and nobody opened an issue about it (nor there were tests for that option).
  • Added contextRequest option from #25, thanks to @amazzeo
  • A bit of documentation revamp, feedback is welcome

0.6.0: Joi dependency moved to peerDependencies, it has to be installed at the same depth as express-validation. This is to avoid having to bump library version to update Joi.

0.5.0: req objects gets parsed. Joi validates the body, params, query, headers or cookies and returns a Javascript Object.

0.4.5: support for Joi.ref inside arrays, refer to #17 for an example

0.4.4: support for Joi any.default, thanks to @iheanyi

0.4.3: added cookies validation, thanks to @aymericbeaumet.

0.4.2: errors have now a types array (full reference in Joi source), similar to messages, useful to sum up errors for internationalization purposes.

0.4.1: added options() method to globally override configuration.

0.4.0: express-validation now returns a ValidationError, not a simple Error. This offer some advantages when writing error handlers.

0.3.0: prior to version 0.3.0, we returned a json error response straight out of the middleware, this changed in 0.3.0 to allow the express application itself to return the error response. So from 0.3.0 onwards, you will need to add an express error handler, and return an error response.

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

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