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Email Validation in JavaScript: Guide

Email Validation in JavaScript: Guide

In this blog post, we will learn about email validation in JavaScript. We’ll explore the techniques and best practices to verify email addresses, prevent errors, and enhance the overall quality of your email communication. Whether you’re a seasoned developer or a newcomer to JavaScript, this blog will provide you with the knowledge to validate email addresses successfully, saving you time and improving your email delivery rates. 

Table of Contents

What is Email Validation in JavaScript?

Email validation in JavaScript is a process where we use JavaScript code to check if an email address you enter is correctly formatted. It looks for things like the “@” symbol, domain name, and the ending part (like “.com“). It also checks for certain special characters.

Typical email validation in javascript tasks are:

  • Checking for the “@” Symbol
  • Domain (e.g., “example.com”)  and Top Level Domain (e.g., “.com”) Validation 
  • Lower and Upper Case Insensitivity
  • Basic Length Check

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How to Validate Emails Using JavaScript

Email validation is a important part of validating an HTML form. Before we start regex patterns for email validation in JavaScript, let’s break down the structure of a typical email address:

  1. Local Part: This is part of the email address before the “@” symbol. It can contain letters, numbers, and special characters like dots and underscores.
  2. Domain Part: This is the domain name after the “@” symbol. It consists of a series of domain labels separated by dots, with each label containing letters, numbers, and hyphens.
  3. Top-Level Domain (TLD): This is the last part of the domain, like “.com,” “.org,” or “.net.

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Regular Expressions for Email Validation (Regex)

A basic regex pattern for email validation in JavaScript can be constructed using the following elements:


Let’s break down this pattern:

  • ^ and $: These symbols represent the start and end of the string, ensuring that the entire string is matched.
  • [\w\.-]+: This part matches one or more word characters (letters, numbers, or underscores), dots, or hyphens in the local part of the email address.
  • @: Matches the “@” symbol literally.
  • [\w\.-]+: Similar to the local part, this matches one or more word characters, dots, or hyphens in the domain part.
  • \.: Matches a literal dot before the top-level domain.
  • \w+: Matches one or more word characters for the TLD.


This HTML code creates a form for email validation in JavaScript. It features an input field for users to type their email and a button that, when clicked, activates the JavaScript function to validate the email. This setup is essential for client-side email validation using JavaScript


<!DOCTYPE html>
<html lang="en">
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Email Validation</title>
    <label for="email">Enter your email address:</label>
    <input type="text" id="email" name="email">
    <button type="button" onclick="validateEmail()">Validate Email</button>

This below JavaScript code is designed for email validation in a web application. It defines a function validateEmail() that:

  • Retrieves the email address entered by the user from the input field.
  • Uses a regular expression (regex) to define the valid format for an email address.
  • Checks if the entered email matches this regex pattern.
  • Displays an alert to the user indicating whether the email address is valid or invalid.


    function validateEmail() {
      // Get the entered email address
      var email = document.getElementById("email").value;
      // Regular expression for email validation
      var regex = /^[\w\.-]+@[\w\.-]+\.\w+$/;
      // Test if the entered email matches the regex pattern
      var isValid = regex.test(email);
      // Display the result to the user
      if (isValid) {
        alert("Valid email address!");
      } else {
        alert("Invalid email address. Please enter a valid email.");

Output 1

Regular Expressions for Email Validation (Regex)

Output 2

Regular Expressions for Email Validation (Regex)

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Index Value Calculation Method

In JavaScript, there are two functions, `lastIndexOf()` and `indexOf()`, that help you find where certain pieces of text are in a string (like a sentence or a word).

1. `lastIndexOf()`: This function helps you find where a specific piece of text shows up for the last time in a string. It starts looking from the beginning and goes to the end. If it finds the text, it tells you its position, starting from 0 (so, the first position is 0, the second is 1, and so on). If it can’t find the text, it gives you -1. This function cares about uppercase and lowercase letters being different.

2. `indexOf()`: This function is similar, but it finds where a specific piece of text appears for the first time in a string. It also gives you the position starting from 0, or -1 if it can’t find the text. Like `lastIndexOf()`, it also treats uppercase and lowercase letters as different.

When checking email addresses in JavaScript, you can use these functions to make sure the email has an “@” and a “.” in the right places. This is a basic way to check if an email address looks like it’s in the right format.


This HTML document provides a basic structure for an email validation example using JavaScript. It includes a text input field for users to enter their email and a button that, when clicked, triggers the JavaScript function validateEmail() for client-side email validation. This setup is a straightforward example of implementing email validation in JavaScript within a web application.


<!DOCTYPE html>
    <title>Email Validation Example</title>
    <h2>Email Validation Example</h2>
    <input type="text" id="email" placeholder="Enter your email">
    <button onclick="validateEmail()">Validate Email</button>

This below JavaScript code is a function for email validation in a web application. It checks the format of an email entered into an input field, using specific conditions to ensure the email’s validity. The function is a key part of client-side email validation in JavaScript, providing immediate feedback on whether the entered email meets the standard format requirements.


// Function to validate the email address
function validateEmail() {
    // Retrieve the value from the input field with id 'email'
    var email = document.getElementById("email").value;
    // Find the position of the '@' character
    var atPosition = email.indexOf("@");
    // Find the position of the last '.' character
    var dotPosition = email.lastIndexOf(".");
    // Check if the '@' is in a valid position, and if the last '.' is in a valid position
    if (atPosition < 1 || dotPosition < atPosition + 2 || dotPosition + 2 >= email.length) {
        // If any condition is not met, show an alert indicating the email is invalid
        alert("Please enter a valid email address.");
    } else {
        // If all conditions are met, show an alert indicating the email is valid
        alert("Email address is valid.");

Output 1

Index Value Calculation Method

Output 2

Index Value Calculation Method


In conclusion, our journey through the complications of email validation in JavaScript has provided you with both the understanding and tools necessary to implement this important feature in web applications. We started by exploring the importance of email validation, highlighting its role in user data integrity and the overall user experience. We explored how ‘regex’ can be used to create a flexible pattern for validating email formats, capturing a wide range of email idiosyncrasies. Following this, we shifted our focus to the more traditional methods of string manipulation using ‘indexOf()’ and ‘lastIndexOf()’

By now, you should feel confident in your ability to implement email validation in your web projects, increasing functionality and reliability. Remember, the best way to understand is by applying these concepts in real-world scenarios.

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Frequently Asked Questions

Why is email validation important in JavaScript?

Email validation in JavaScript ensures that user-entered email addresses meet the required format, reducing errors and enhancing data integrity.

How can I perform basic email validation using JavaScript?

Use regular expressions in JavaScript to check if an email address follows the standard format, including the presence of “@” and a valid domain.

What are common mistakes to avoid in JavaScript email validation?

Avoid overlooking the importance of validating both the format and domain of an email address. Regularly update validation patterns to adapt to changing standards.

Can JavaScript alone prevent all invalid email submissions?

While JavaScript can catch most format errors, server-side validation is crucial for security and to prevent manipulation, as clients can disable or bypass JavaScript.

Are there JavaScript libraries for advanced email validation?

Yes, libraries like “validator.js” provide comprehensive email validation features, simplifying the process and ensuring accuracy in handling complex email scenarios.

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About the Author

Principal Data Scientist

Meet Akash, a Principal Data Scientist who worked as a Supply Chain professional with expertise in demand planning, inventory management, and network optimization. With a master’s degree from IIT Kanpur, his areas of interest include machine learning and operations research.