====== Getting Started ======

express-validator is a set of [[http://expressjs.com/|express.js]] middlewares that wraps [[https://github.com/validatorjs/validator.js|validator.js]] validator and sanitizer functions.

===== Installation =====

Install it using npm (make sure that you have Node.js 8 or newer):

<code powershell>
npm install --save express-validator
</code>

===== Basic guide =====

> It's recommended that you have basic knowledge of the express.js module before you go on with this guide. 

Let's get started by writing a basic route to create a user in the database:

JavaScript

<code javascript>
const express = require('express');
const app = express();
app.use(express.json());
app.post('/user', (req, res) => {
    User.create({    
        username: req.body.username,    
        password: req.body.password,  
    }).then(user => res.json(user));});
</code>

TypeScript
<code javascript>
import express from 'express';

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

app.post('/user', (req: express.Request, res: express.Response) => {  
    User.create({    
        username: req.body.username,    
        password: req.body.password,  
    }).then(user => res.json(user));});
</code>

Then, you'll want to make sure that you validate the input and report any errors before creating the user:

JavaScript

<code javascript>
// ...rest of the initial code omitted for simplicity.
const { body, validationResult } = require('express-validator');

app.post(  
    '/user',  
    // username must be an email  
    body('username').isEmail(),  
    // password must be at least 5 chars long  
    body('password').isLength({ min: 5 }),  (req, res) => {    
        // Finds the validation errors in this request and wraps them in an object with handy functions    
            const errors = validationResult(req);    
            if (!errors.isEmpty()) {      
                return res.status(400).json({ errors: errors.array() });    
            }    
            
            User.create({      
                username: req.body.username,     
                password: req.body.password,    
            }).then(user => res.json(user));  
            },
    );
</code>

TypeScript
<code javascript>
// ...rest of the initial code omitted for simplicity.
import { body, validationResult } from 'express-validator';

app.post(
  '/user',
  // username must be an email
  body('username').isEmail(),
  // password must be at least 5 chars long
  body('password').isLength({ min: 5 }),
  (req: express.Request, res: express.Response) => {
    // Finds the validation errors in this request and wraps them in an object with handy functions
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
      return res.status(400).json({ errors: errors.array() });
    }

    User.create({
      username: req.body.username,
      password: req.body.password,
    }).then(user => res.json(user));
  },
);
</code>

Voila! Now, whenever a request that includes invalid ''username'' or ''password'' fields is submitted, your server will respond like this:

<code javascript>
{
  "errors": [
    {
      "location": "body",
      "msg": "Invalid value",
      "param": "username"
    }
  ]
}
</code>

For all the available validators in express-validator (just like its options), take a look at validator.js docs [[https://github.com/validatorjs/validator.js#validators|here]].

===== What's next =====

This completes the basic guide on getting started with express-validator.\\ You might want to continue reading about some of the more advanced features available:

  * [[:docs:sanitization|Sanitization]]
  * [[:docs:custom-validators-sanitizers|Custom validators/sanitizers]]
  * [[:docs:custom-error-messages|Custom error messages]]
  * [[:docs:wildcards|Wildcards]]
  * [[:docs:schema-validation|Schema validation]]

[[:docs:sanitization|Sanitization]][[:docs:sanitization| ]][[:docs:sanitization|→]]