How to Create a Login Form with Ajax

See Ajax: Tips and Tricks for similar articles.

An Ajax login form can send data to the server and display an error message without requiring a page refresh. This can make the process of logging in less painful for the user. Here's how to program an Ajax login form.

  1. Create an HTML document.
    <!DOCTYPE html>
    <html lang="en">
        <meta charset="UTF-8">
  2. Create a script block inside your document and write a function named login() that will make the Ajax request when the form is submitted.
    function login(form) {
        var un = form.Username.value;
        var pw = form.Password.value;
        var xmlhttp = new XMLHttpRequest();"post", "Login", true);
        xmlhttp.onreadystatechange = function () {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
  3. Write an event listener that will register an eventListener for the form when the page loads.
    window.addEventListener(window,"load", function() {
        var loginForm = document.getElementById("LoginForm");
        window.addEventListener(loginForm, "submit", function() {
  4. Create a form.
    <form id="LoginForm" onsubmit="return false">
        <h1>Login Form</h1>
        <div class="FormRow">
            <label for="Username">Username:</label>
            <input type="text" size="15" id="Username" name="Username">
        <div class="FormRow">
            <label for="Password">Password:</label>
            <input type="password" size="15" id="Password" name="Password">
        <div class="FormRow" id="LoginButtonDiv">
            <input type="submit" value="Login">
        <div id="BadLogin">
            <p>The login information you entered does not match
            an account in our records. Please try again.</p>
  5. Write a function to receive the results of the Ajax login and display the response text.
    function loginResults() {
        var loggedIn = document.getElementById("LoggedIn");
        var badLogin = document.getElementById("BadLogin");
        if (xmlhttp.responseText.indexOf("failed") == -1) {
            loggedIn.innerHTML = "Logged in as " + xmlhttp.responseText;
   = "block";
   = "none";
        } else {
   = "block";
            form.Username.className = "Highlighted";
            setTimeout(function() {
       = 'none';
            }, 3000);
  6. Test the form. This example code assumes that your login script is available at /Login, relative to the location of the script. You can customize the Login function and the path to your script for your own needs. Result of Running the Demo Scripts

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