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

<!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

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 incomming 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) 
}) 

Steps to run the program:

The project structure will look as shown below:
Make sure you have a ‘view engine’. We have used “ejs” and also install express and express-validator, body-parser using following commands:
```
npm install ejs
```
```
npm install express
```
```
npm install body-parser
```
```
npm install express-validator
```
Run index.js file using below command:
```
node index.js
```
Open the browser and type this URL http://localhost:8080/, the fill this sample form with correct data as shown below:
Then submit the form and if no error occurs, then you will see the following output:
And if you try to submit the form with incorrect data, then you will see the error message as shown below:

My Personal Notes

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