How-To: Tutorial Javascript (JS): Creating a Modal (1 Viewer)


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May 5, 2018
New York, USA
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Ever wondered how the popup window is created when you click on a login button on a web page? This post will give you a quick tutorial.

Bonus: Use CSS to give your login box more definition.

I recommend separating your CSS/HTML/PHP/Javascript into separate files. It will make them more manageable. Create the following files for this tutorial in its own folder:
  1. index.html
  2. style.css
  3. main.js

  <TITLE>Test Modal</TITLE>
  <!-- Reference your stylesheet here-->
  <!-- Create the button that triggers the modal -->
  <button id="modalBtn">Login</button>

  <!-- Create the Modal Container. Give your container an id by using the id tag. You also need to assign a class to your container
to set your properties from your CSS file.-->
  <div id="loginModal" class="modal">

   <!-- This will hold your Modal Content. You will also want to assign a class to your content  container for additional properties that will be applied to this container ONLY.-->
   <div class="modal-content">
    <span class="close">&times;</span>
    <form action="">
     Username:<input type="text"><br>
     Password:<input type="password"><br>
     <input type="submit" value="submit">
 <!-- Reference your Javascript file here -->
/* The Modal (background) */
.modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1; /* Sit on top */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    overflow: auto; /* Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.4); /* Black w/ opacity */

/* Modal Content/Box */
.modal-content {
    background-color: #fefefe;
    margin: 15% auto; /* 15% from the top and centered */
    padding: 20px;
    border: 1px solid #888;
    width: 80%; /* Could be more or less, depending on screen size */

/* The Close Button */
.close {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;

.close:focus {
    color: black;
    text-decoration: none;
    cursor: pointer;
// Get the modal
var modal = document.getElementById('loginModal');

// Get the button that opens the modal
var btn = document.getElementById("modalBtn");

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks on the button, open the modal 
btn.onclick = function() { = "block";

// When the user clicks on <span> (x), close the modal
span.onclick = function() { = "none";

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
    if ( == modal) { = "none";

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