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

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)
})