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JavaScript Tutorial: Learn JavaScript from Scratch

Overview

An Introduction to JavaScript: Here Is All You Need to Know

Lesson - 1

JavaScript Hello World: Here's What You Need To Know

Lesson - 2

All You Need to Know About JavaScript Arrays

Lesson - 3

Using Array Filter In JavaScript to Filter Array Elements

Lesson - 4

Everything You Need to Know About Array Reduce JavaScript

Lesson - 5

Introduction To JavaScript Loops: Do-While, For, For-In Loops

Lesson - 6

All You Need to Learn About Javascript Functions

Lesson - 7

The Best Guide on How to Implement JavaScript Closures

Lesson - 8

JavaScript “This” Keyword and How to Implement It

Lesson - 9

How to Implement JavaScript Form Validation

Lesson - 10

An Introduction Guide To JavaScript RegEx

Lesson - 11

How to Do an Email Validation in JavaScript?

Lesson - 12

All You Need to Know About JavaScript Promises

Lesson - 13

How to Implement JavaScript Async/Await

Lesson - 14

JavaScript DOM Tutorial: 2020 Edition

Lesson - 15

JavaScript Objects: Properties, Methods, and Accessors

Lesson - 16

An Introduction to Javascript Games: The Best Guide

Lesson - 17

An Easy Guide to Build a Calculator App in JavaScript

Lesson - 18

Javascript Projects: The Best Guide

Lesson - 19

What is OOP in JavaScript? How is it Implemented?

Lesson - 20

The Best Guide to Understanding JavaScript Learning Path

Lesson - 21

Java Vs .NET: Which Is the Best Technology to Choose?

Lesson - 22

Top 80+ JavaScript Interview Questions and Answers for 2024

Lesson - 23

Typeof in JavaScript: Checking Data Types Using the Typeof Operator

Lesson - 24

Tips and Tricks That You Should Know Before Going to a Coding Interview

Lesson - 25

Callback Functions in JavaScript: Everything You Need to Know

Lesson - 26

JavaScript Events

Lesson - 27

How to Implement JavaScript Form Validation

Lesson 10 of 27By Chinmayee Deshpande

Last updated on Jul 16, 202416703
How to Implement JavaScript Form Validation

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A web application is generally interactive, be it in the case of registration, surveys, or feedback. The application should also be smart enough to validate the information being provided by the user. JavaScript Form Validation does precisely this. 

Form validation, as the name proposes, checks, if the information provided, is accurate or not. This can be done on the server-side; however, the process takes longer. JavaScript facilitates form validation on the client-side before sending it over to the server, thus improving the processing speed. 

Form validation typically involves two functions: 

  1. Basic Validation: This warrants that all the mandatory fields are filled. It would require just a loop through each field in the form and check for data.
  2. Data Format Validation: Data validation checks the data for its correctness. Your code must include appropriate logic to test the accuracy of data.

Now that you know why form validation is necessary let us take the plunge and look into the process of creating a simple form and validating the information.

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The demo use case involves the basic validation of the email and passwords fields, i.e., it checks if the information is provided by the user or not. For that, we’ve created a form using the <form> tag by HTML. Once the form is submitted, a welcome message is displayed. 

<form name="myForm" action="message.html" onsubmit="return(validate());">

         <input type="text" placeholder="Email" name="EMail" /><br>

        <input type="text" placeholder = "Password" name="Password" /><br>

        <button type="submit">Submit</button>

The <form> tag has attributes like the name, which specifies the name of the form, and action, that specifies the action to be performed when submitted. And submit, which specifies the function that is being called to validate the form. 

Within the input tag, the name of the field along with its type and a placeholder is mentioned. The input fields for email and password are created. Finally, a button is created for the form submission.

function Validate(){

           if(document.myForm.EMail.value ==""){

               alert("Please provide your Email ID");

               document.myForm.EMail.focus()

               return false

           }else if(document.myForm.Password.value ==""){

            alert("Please provide your Password");

               document.myForm.Password.focus()

               return false

           }

           else {

               return true

           }

       } 

The validate() method is a vital part of the program. It first checks if the email field is empty. If yes, it alerts the user and focuses on the email field for the input. It then checks if the password field is filled. If not, it alerts the user regarding the same. Both the above cases return false and terminate the function. However, if the user fills in their credentials, the function returns true. 

Please note that if the function returns false, the form does not get submitted. 

The message.html is a file displaying a simple welcome message. Here’s the code for it. 

<html>

    <head>

        <title>Form Validation</title>

        <script type = "text/JavaScript">

        

        </script>

    </head>

    <body>

        <h1>Hello there! Welcome :) </h1>

    </body>

</html>

This is the output of the code if no information is provided: 

/validation-1

      JavaScript Form Validation

This is the output if the email field is filled without the password field:

/validation-2

      JavaScript Form Validation

This is the output of the code if both the fields are provided: 

/val-3

      JavaScript Form Validation 

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Next Steps

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About the Author

Chinmayee DeshpandeChinmayee Deshpande

Chinmayee is a Research Analyst and a passionate writer. Being a technology enthusiast, her thorough knowledge about the subject helps her develop structured content and deliver accordingly.

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