Make Pop-Up Modal Window In Vanilla JavaScript

Learn how to create a simple responsive pop-up modal window using Vanilla JavaScript along with HTML and CSS with a bit of Flexbox.

• Create A Button That Opens Pop Up Modal Window
• Create Pop Up Modal Overlay
• Center Pop Up Modal Window To The Modal Overlay
• Open Up Pop Up Modal Window On Button Click
• Close/Hide Pop Up Modal Window On Button Click
• Hide Pop Up Modal Window When Modal Overlay Is Clicked

Create A Button That Opens Pop Up Modal Window

Declare a <button> HTML element with an id open-modal.

<button id="open-modal">Open Modal Window</button>

The goal is when a user presses this button, the pop-up modal window will open.

Style the button using CSS Flexbox and centre it on the screen.

* {
    margin: 0;
    padding: 0;
    font-family: Arial, Helvetica, sans-serif;
    box-sizing: border-box;
}

body {
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

button {
    padding: 10px;
    font-size: 1.1em;
    background: #32bacf;
    color: white;
    border: none;
    border-radius: 10px;
    border: 1px solid rgba(0, 0, 0, 0.2);
    cursor: pointer;
}

button:hover {
    background: rgba(0, 0, 0, 0.7);
}

Create Pop-Up Modal Overlay

Normally, pop-up modal windows have overlays with a transparent darker background that covers entire browser screen.

Define a div with an id model-overlay which will cover the entire screen.

<div id="modal-overlay">
<div>

Then, make it to full screen using height:100vh CSS property.

Bring it in front of the button by using position:absolute with a transparent background colour.

#modal-overlay {
    width: 100%;
    height: 100vh;
    position: absolute;
    background: rgba(0, 0, 0, 0.7);
}

I just added the border to see the boundaries of the modal-overlay element.

Center Pop-Up Modal Window To The Modal Overlay

Create a div with an id modal inside the modal-overlay element, which will be an actually pop-up modal window that user interacts with.

<div id="modal-overlay">
  <div id="modal">
  </div>
<div>

Add CSS style to make it visible on the screen.

Adding width:100% and max-width:650px will make sure the width of the pop-up modal window won’t exceed when the browser width is more than 650px.

If the browser width is less than 650px, the pop-up modal window will stretch the width to fill the screen which is normally for mobile viewports.

#modal-overlay #modal {
    max-width: 650px;
    width: 100%;
    background: white;
    height: 400px;
}

Centre the pop-up modal window to the screen using Flexbox.

To do that, just add the three lines of Flexbox code to the modal-overlay which are

• display:flex → Convert an HTML element to Flexbox
• align-items:center → centre the pop-up modal window vertically to the viewport
• justify-content:center → centre the pop-up modal window horizontally to the viewport

#modal-overlay {
   ...
  
   display: flex;
   align-items: center;
   justify-content: center;
}

Open Up Pop-Up Modal Window On Button Click

Now we have the basic pop-up modal window designed using CSS.

Make it visible when a user presses the open modal button.

To do that,

First, hide the modal overlay by default by changing its display property from flex to none.

#modal-overlay {
   ...
  
   display: none; // Changed from flex to none
   align-items: center;
   justify-content: center;
}

Create a DOM reference to the open-modal button as well as the modal-overlay elements.

const openModalButton = document.getElementById("open-modal");
const modalWindowOverlay = document.getElementById("modal-overlay");

Attach a click event to the openModalButton with the callback arrow function showModalWindow.

const showModalWindow = () => {
    modalWindowOverlay.style.display = 'flex';
}

openModalButton.addEventListener("click", showModalWindow);

Set the display property of the modalWindowOverlay to flex inside showModalWindow() function which will open up the modal window.

As you can see, there is no way we can close/hide the pop-up modal window after its became visible on the screen.

Let’s fix it!

Close/Hide Pop-Up Modal Window On Button Click

Typically, there will be a close button on the top or bottom right side of the pop-up modal window.

Let’s add a close button on the bottom left side of the modal window.

Define header, content and footer HTML elements inside the pop-up modal window.

<div id="modal">

    <div class="modal-header">
        <h2>Modal Pop Up Window</h2>
    </div>

    <div class="modal-content">
        <p>Modal Content</p>
    </div>
    
    <div class="modal-footer">
        <button id="close-modal">Close</button>
        <button>Save</button>
    </div>

</div>

Generally, you’ll have two buttons on the footer of the pop-up modal window, which may be save and close.

Let’s push the buttons to the bottom using Flexbox.

Turn the display property of the pop-up modal window to flex and set the flex direction to column.

Set margin-top to auto to the .modal-footer element which pushes the buttons to the bottom.

#modal-overlay #modal {
    max-width: 650px;
    width: 100%;
    background: white;
    height: 400px;

    display: flex;
    flex-direction: column;
    padding:10px;
}

#modal-overlay #modal .modal-footer {
    margin-top: auto;
}

Let’s hide the pop-up modal window when the user presses the close button.

Define a DOM reference of the close button.

Attach a click event to the close button with the call back function hideModalWindow.

Declare hideModalWindow function and set the display property of modalWindowOverlay to none inside it.

const closeModalButton = document.getElementById("close-modal");

const hideModalWindow = () => {
    modalWindowOverlay.style.display = 'none';
}

closeModalButton.addEventListener("click", hideModalWindow);

Hide Pop-Up Modal Window When Modal Overlay Is Clicked

In addition to the close button, you often see the pop-up modal window will be closed or hidden when the user clicks away from it.

To do that, we need to identify if a user clicks the actual pop-up modal window and its content inside or the modal overlay that covers the entire screen.

To check that,

Attach a click event to the #modal-overlay with a callback function hideModalWindowOnBlur

modalWindowOverlay.addEventListener("click", hideModalWindowOnBlur)

Using e.target and e.currentTarget properties of an event object we can identify where a user clicks when the pop-up modal window is visible on the screen.

e.target will capture a clicked HTML element which can be either the parent or child elements.

The parent element will be referred to an element that has a click event attached to.

In this case, the #modal-overlay.

The child elements will be referred to all the HTML elements right inside the parent element.

On the other hand, e.currentTarget will only get the parent element regardless of where user clicks either parent or child elements.

In this case the #modal-overlay.

This way we can determine whether a user clicks the #modal-overlay or the actual pop-up modal window.

If a user presses the modal overlay, hide/close it by checking if e.target value is equal to e.currentTarget.

const hideModalWindowOnBlur = (e) => {

    if(e.target === e.currentTarget) {
        hideModalWindow();
    }
}

Try it out ⛹️

See the Pen Make Pop-Up Modal Window In Vanilla JavaScript {Try it out} by Raja Tamil (@rajarajan) on CodePen.

If you’ve any question or suggestion about this article, feel free to reach out to me by commenting below and I’ll read and reply each and every one of them.

I’m looking forward to hearing from you.

Happy coding…