Login form plays a key role in website development, which authenticate user access to other resources.

Here, we are giving our JavaScript codes for validating Login form. In our example, we have a login form with two input fields i.e. username and password, As user clicks on login button, JavaScript validation function comes into act.

Moreover, we allowed three attempts for user to login, after third attempt all fields get disabled.

var attempt = 3; //Variable to count number of attempts
attempt --; //Decrementing by one
document.getElementById("username").disabled = true;
document.getElementById("password").disabled = true;
document.getElementById("submit").disabled = true;
return false;


Below is our complete code with download and live demo option

validating login form using javascript

HTML File: javascript_login.html

Here, we have created a simple HTML form with some fields, as user clicks submit button JavaScript code will execute.

<title>Javascript Login Form Validation</title>
<!-- Include CSS File Here -->
<link rel="stylesheet" href="css/style.css"/>
<!-- Include JS File Here -->
<script src="js/login.js"></script>
<div class="container">
<div class="main">
<h2>Javascript Login Form Validation</h2>
<form id="form_id" method="post" name="myform">
<label>User Name :</label>
<input type="text" name="username" id="username"/>
<label>Password :</label>
<input type="password" name="password" id="password"/>
<input type="button" value="Login" id="submit" onclick="validate()"/>
<span><b class="note">Note : </b>For this demo use following username and password. <br/><b class="valid">User Name : Formget<br/>Password : formget#123</b></span>


Javascript File: login.js

Given below is our complete JavaScript code.

var attempt = 3; // Variable to count number of attempts.
// Below function Executes on click of login button.
function validate(){
var username = document.getElementById("username").value;
var password = document.getElementById("password").value;
if ( username == "Formget" && password == "formget#123"){
alert ("Login successfully");
window.location = "success.html"; // Redirecting to other page.
return false;
attempt --;// Decrementing by one.
alert("You have left "+attempt+" attempt;");
// Disabling fields after 3 attempts.
if( attempt == 0){
document.getElementById("username").disabled = true;
document.getElementById("password").disabled = true;
document.getElementById("submit").disabled = true;
return false;


CSS File: style.css

Styling of HTML elements.

/* Below line is used for online Google font */
@import url(http://fonts.googleapis.com/css?family=Raleway);
background-color: #FEFFED;
padding: 30px 35px;
margin: -10px -50px;
border-radius: 10px 10px 0 0;
margin: 10px -50px;
border: 0;
border-top: 1px solid #ccc;
margin-bottom: 40px;
width: 900px;
height: 610px;
margin:35px auto;
font-family: 'Raleway', sans-serif;
width: 300px;
padding: 10px 50px 25px;
border: 2px solid gray;
border-radius: 10px;
font-family: raleway;
width: 100%;
height: 40px;
padding: 5px;
margin-bottom: 25px;
margin-top: 5px;
border: 2px solid #ccc;
color: #4f4f4f;
font-size: 16px;
border-radius: 5px;
color: #464646;
text-shadow: 0 1px 0 #fff;
font-size: 14px;
font-weight: bold;
text-decoration: none;
border: 1px solid rgb(0, 143, 255);
background-color: rgb(0, 214, 255);
padding: 3px 20px;
border-radius: 2px;
color: black;
font-size: 16px;
background: linear-gradient(#ffbc00 5%, #ffdd7f 100%);
border: 1px solid #e5a900;
color: #4E4D4B;
font-weight: bold;
cursor: pointer;
width: 100%;
border-radius: 5px;
padding: 10px 0;
background: linear-gradient(#ffdd7f 5%, #ffbc00 100%);

Pabbly Form Builder


Hence, we have applied JavaScript validation on login form, you can also use database to verify user. Hope you like it, keep reading our other blogs in future.