How to Validate Data using express-validator Module in Node.js ?

Validation in node.js can be easily done by using the express-validator module. This module is popular for data validation. There are other modules available in market like hapi/joi, etc but express-validator is widely used and popular among them.
Steps to install express-validator module:

You can install this package by using this command.

npm install express-validator

After installation, you can check your express-validator module version in command prompt using the command.

npm version express-validator

After that, you can just create a simple data as shown below to send the data to the server.
Filename: SampleForm.ejs

html

<!DOCTYPE html>
<html>
    <head>
        <title>Validation using Express-Validator</title>
    </head>
<body>
<h1>Demo Form</h1>
  
<form action="saveData" method="POST">
  <pre>
      Enter your Email    : <input type="text" name="email"> <br>
      Enter your Name     : <input type="text" name="name"> <br>
      Enter your Number   : <input type="number" name="mobile"> <br>
      Enter your Password : <input type="password" name="password"> <br>
      <input type="submit" value="Submit Form">
  </pre>
</form>
  
</body>
</html>

After that, you can just create a file, for example index.js as show below:
Filename: index.js

javascript

const { check, validationResult }
    = require('express-validator');
 
const bodyparser = require('body-parser')
const express = require("express")
const path = require('path')
const app = express()
 
var PORT = process.env.port || 3000
 
// View Engine Setup
app.set("views", path.join(__dirname))
app.set("view engine", "ejs")
 
// Body-parser middleware
app.use(bodyparser.urlencoded({ extended: false }))
app.use(bodyparser.json())
 
app.get("/", function (req, res) {
    res.render("SampleForm");
})
 
// check() is a middleware used to validate
// the incoming data as per the fields
app.post('/saveData', [
    check('email', 'Email length should be 10 to 30 characters')
                    .isEmail().isLength({ min: 10, max: 30 }),
    check('name', 'Name length should be 10 to 20 characters')
                    .isLength({ min: 10, max: 20 }),
    check('mobile', 'Mobile number should contains 10 digits')
                    .isLength({ min: 10, max: 10 }),
    check('password', 'Password length should be 8 to 10 characters')
                    .isLength({ min: 8, max: 10 })
], (req, res) => {
 
    // validationResult function checks whether
    // any occurs or not and return an object
    const errors = validationResult(req);
 
    // If some error occurs, then this
    // block of code will run
    if (!errors.isEmpty()) {
        res.json(errors)
    }
 
    // If no error occurs, then this
    // block of code will run
    else {
        res.send("Successfully validated")
    }
});
 
app.listen(PORT, function (error) {
    if (error) throw error
    console.log("Server created Successfully on PORT ", PORT)
})