How to validate user input by using express validator

by shivanisanju03 Updated: Mar 9, 2023

Guide Kit

The best way to handle validation on any kind of input coming from outside in Express is by using the express-validator package: You require the check and validationResult objects from the package: We pass an array of check () calls as the second argument of the post () call. Every check () call accepts the parameter name as argument.

In order to validate a file input field you could use multer: middleware that adds a body object and a file object to the request object. And then use express-validator .custom () validation function chained to your validation middleware.

Here is an example of how to validate user input by using express validator

Fig 1: Preview of the output that you will get on running this code from your IDE.

Code

Can't validate user input by using Express-validator

JavaScriptLines of Code : 57License : Strong Copyleft (CC BY-SA 4.0)

Dependent Libraries :

const express = require('express');
const app = express();
const bodyParser = require('body-parser');
const expressValidator = require('express-validator');

app.use(express.static('./'));
app.use(bodyParser.urlencoded({ extended: true }));
app.use(expressValidator());

var router = express.Router();
app.use("/", router);

router.post('/register', function(req, res, next) {
    console.log('/register POST body: ', req.body);

    /* Check form variables. */
    req.checkBody('name', 'Name is required').notEmpty();
    req.checkBody('userpass', 'Pass is required').notEmpty();

    var errors = req.validationErrors();
    if (errors) {
        console.error("Validation errors occurred: ", errors);
        res.status(400).json({ status: "Bad Request" });
        return;
    }

    console.log("Validation successful");

    // Get user input from register form
    let nam = req.body.name;
    let pass = req.body.userpass;

    var newUser = new User({
        username:nam,
        pass:pass
    });
    User.createUser(newUser,function(err,user){
            if(err) throw err;
            console.log(user);
    });
    res.location('/register');
    res.redirect('/register');
});

app.listen(3000);

<!doctype html>
<html lang="en">
    <body>
    <form  action="/register" method="POST">
        <input type="text" name="name" placeholder="username"><br>
        <input type="password" name="userpass" placeholder="password"><br>
        <input type="submit" name="submit" value="send">
    </form>
    </body>
</html>

Instructions

Follow the steps carefully to get the output easily.

Install Visual Studio Code IDE on your computer.
Create a new HTML file.
Copy the code using the 'Copy' button and create an HTML tag then paste the code inside the tag into that HTML file.
Create a new JS file copy the JS code and paste the code (refer to preview as well).
Save and run the file directly from the file location to generate the output.

I found this code snippet by searching for ' input validations using express js' you can try any such use case!

Environment tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

The solution is created in Visual Studio Code 1.75.1.

Using this solution, we are able to process how to validate user input by using express validator with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to process how to validate user input by using express validator .

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