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Client-Side Form Validation With Javascript

12th June 2020 6 mins read

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In this article, you will learn how to do client-side form validation and why it's very crucial for your web development with jQuery Validation Javascript library.

Code available in GitHub @ Client-Side Form Validation

We will cover the following

Why To Perform Client Side Validation?
Download Validation Library
Example Folder Structure
Basic Form Validation
Custom Validation Rules & Messages
Form Handlers
Available Validation Rules

1) Why To Perform Client Side Validation?

Client-side validation is very important because

Can be used along with any web-based programming languages.
No need to send form data to your server to validate and then return back to customer browser and display it. If we handle it in client-side ie browser end of user then we can overcome the whole process and improve user experience.
Nowadays all browsers are Javascript enable with some user exceptional cases. So implementation will be very easy.
Rapid validation implementation ie, once you get good grip on the library it won't take more than 10 minutes to implement even for the lengthier form you have.

2) Download Validation Library

We will be using jQuery Validator Javascript library for client-side validation. You can either download the library by going to the URL and add it in your project or you can use CDN for faster loading.

Note: Once you to to the above URL and scroll down then you will get CDN link.

3) Example Folder Structure

We will be using the following folder structure just for the sake of demonstration.

js/
  |_ jquery-validator.js
  |_ jquery.js

index.html

js (Folder) - Keep our JS library files

js/jquery-validator.js - jQuery validation library

js/jquery.js - jQuery library

index.html - Validation demo

4) Basic Form Validation

First, let's create a form so that we can add some validation to it. The following is the basic HTML form.

index.html

<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Client Side Validation</title>
        <style>
            body{ padding-top: 50px; padding-left: 100px; }
            .error { color: red; }
        </style>
    </head>
    <body>
        <form id="demo-form">
            <div>
                <label for="fullname">Full Name *</label> <br>
                <input type="text" class="form-control" name="fullname" required>
            </div>
            <br>            
            <div>
                <label for="email">Email *</label> <br>
                <input type="email" class="form-control" name="email" required>
            </div>
            <br>
            <div>
                <label for="contactMethod">Preferred Contact Method *</label> <br>
                <p>
                    Email: <input type="radio" name="contactMethod" id="contactMethodEmail" value="Email" required="">
                    Phone: <input type="radio" name="contactMethod" id="contactMethodPhone" value="Phone">
                </p>
            </div>
            <br>
            <div>
                <label for="hobbies">Hobbies (Optional, but 2 minimum):</label> <br>
                <p>
                    Skiing <input type="checkbox" name="hobbies[]" id="hobby1" value="ski"><br>
                    Running <input type="checkbox" name="hobbies[]" id="hobby2" value="run"><br>
                    Eating <input type="checkbox" name="hobbies[]" id="hobby3" value="eat"><br>
                    Sleeping <input type="checkbox" name="hobbies[]" id="hobby4" value="sleep"><br>
                    Reading <input type="checkbox" name="hobbies[]" id="hobby5" value="read"><br>
                    Coding <input type="checkbox" name="hobbies[]" id="hobby6" value="code"><br>
                </p>
            </div>
            <br>            
            <div>
                <p>
                <label for="heard">Heard about us via *</label> <br>
                <select id="heard" required="">
                    <option value="">Choose..</option>
                    <option value="press">Press</option>
                    <option value="net">Internet</option>
                    <option value="mouth">Word of mouth</option>
                    <option value="other">Other..</option>
                </select>
                </p>
            </div>
            <br>
            <div>
                <p>
                <label for="message">Message (20 chars min, 100 max) :</label> <br>
                <textarea id="message" class="form-control" name="message"></textarea>
                </p>
            </div>
            <br>
            <div>
                <input type="submit" class="btn btn-default" value="validate">
            </div>
        </form>
    </body>
</html>

Observe <form id="demo-form">

Form id with demo-form will be latter used to perform the validation.

Basically the above form looks like the following

Basic Form Overview

Adding Validation

<!-- jQuery Library -->
<script src="./js/jquery.js"></script>

<!-- jQuery Validation Library -->
<script src="./js/jquery-validator.js"></script>

<!-- Basic jQuery Validation -->
<script type="text/javascript">
    /** We are using basic id selector which is assigned to form 
    * validate() will validate your form
    */
    $('#demo-form').validate();
</script>

In the above validate() code it will validate your form based on the form elements attributes ie input, select, textarea which will have required, min, max, minlength, maxlength.

Off course you can change the rules and add multiple rules and messages as per your requirement. I will cover in the next section

5) Custom Validation Rules & Messages

You can simply extend the validation with more rules and custom messages in simple way as follows

Usage Overview

$('#demo-form').validate({
    /** Rules for your form fields */
    rules : {
        /** Field name is the name of your input, select, textarea */
        field_name : {
            /** rule_name -> required, value -> true */
            rule_name : value
        }
    },
    /** Adding custom messages to your validation rules */
    messages : {
        /** Field name that you have added in the rules */
        field_name : {
            /** rule_name and its respective message when it gets triggered */
            rule_name : "message"
        }
    }
});

The validation for your form will look like the following

Implementation Example

<!-- jQuery Library -->
<script src="./js/jquery.js"></script>

<!-- jQuery Validation Library -->
<script src="./js/jquery-validator.js"></script>

<!-- Basic jQuery Validation -->
<script type="text/javascript">
    /** We are using basic id selector which is assigned to form 
    * validate() will validate your form
    */
    $('#demo-form').validate({
        /** Rules for your form fields */
        rules : {
            /** Field name is the name of your input, select, textarea */
            /** rule_name -> required, value -> true */
            fullname : {
                required : true,
                minlength: 3
            },
            email : {
                required: true,
                email: true
            },
            contactMethod : {
                required: true
            },
            "hobbies[]" : {
                required: true,
                minlength: 2
            }
        },
        /** Adding custom messages to your validation rules */
        messages : {
            /** Field name that you have added in the rules */
            /** rule_name and its respective message when it gets triggered */
            email : {
                required : "Email field required"
            },
            "hobbies[]" : {
                required : "Please select atleast 2 hobbies",
                minlength: "Please select {0} hobbies"
            }
        }
    });
</script>

6) Form Handlers

Other than then normal form validation you may also use the form handlers to make what should your submit action must perform after successful validation.

You might want to disable the submit button, show some submitting message, and then submit form details via AJAX request or directly.

This can be achieved with the help of submitHandler option as shown below

SubmitHandler

$("#demo-form").validate({
    rules : {
        /** Your form rules */
    },
    messages : {
        /** Rules custom messages */
    },
    /** Submit Handler ie what should happen after form is 
    * successfully validated 
    */
    submitHandler: function(form) {
        // some other code
        // maybe disabling submit button
        // then submit the form
        $(form).submit();
    }
});

7) Available Validation Rules

List of the validation rules that are available are as follows

To know more on other validation details checkout jQuery Validation website.

Conclusion

Hope you enjoyed the article. Please share with your friends.

Code available in GitHub @ Client-Side Form Validation

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AUTHOR

Channaveer Hakari

I am a full-stack developer working at WifiDabba India Pvt Ltd. I started this blog so that I can share my knowledge and enhance my skills with constant learning.

Never stop learning. If you stop learning, you stop growing