Play CSS Animation Only Once Per Website Visit

In folder icon JavaScript Nov 15, 2021

Updated on May 22, 2023

We have animated elements in the hero section of our website, but we do not want to play this animation all the time our users return to the home page where this hero section is. We want to play this CSS animation only once, when the user enters the site, and never again during the current session. How can we achieve that?

Create the Project

Let’s create our project folder! Let’s name it “animation”. From the terminal we type: 

mkdir animation

Let’s change the directory to this project folder: 

cd animation

In our project, we will create three files: index.html, index.js, and index.css.

Write the HTML Code

Now, let’s open the index.html file and add this code: 

<!DOCTYPE html>
<html lang='en'>
  <head>
    <title>Animation</title>
    <link rel="stylesheet" href="index.css">
  </head>
  <body>
    <h1 id ="heading" class="animated">Animated Heading</h1>
    <script src="index.js"></script>
  </body>
</html>

We have a simple document, with only a heading. We've added an “animated” class to this <h1> element. The elements with that class will be animated, according to the rules we’ll set in the index.css file. After the first page load, when the animation has run once, we’ll remove that class name from the element, so that animation won’t play again during the session. We set a “heading” id for this element, so we can select it via JavaScript.

Write THe Animation

Let’s now open our index.css file, to write our animation. It’s a simple animation, the <h1> element will be hidden at first, then will come from the top and land in its normal position.
We’ll call this animation “moveIn”. Let’s specify the CSS rules inside the @keyframes rule: 

@keyframes moveIn {
  0% {
    opacity: 0;
    transform: translateY(-3rem);
  }
  100% {
    opacity: 1;
    transform: translate(0);
  }
}

Now, we apply this animation to the elements that have an “animated” class: 

.animated {
  animation: moveIn 1.5s ease-out;
}

Write the JavaScript Code

Now, when we open our page, the animation will play. If we refresh the page, the animation will play again. To prevent this, we need to write some JavaScript. Let’s open the index.js file!

We want to store an item in the sessionStorage that reminds the browser that our heading has already been displayed to the user, and the animation has run.

We’ll call this item “Heading” and its value will be “displayed”. We do this as soon as the page is loaded: 

window.addEventListener('load', () => {
  if (document.querySelector('#heading') !== null) {
    window.sessionStorage.setItem('Heading', 'displayed');
  }
})

Then we write another function that checks if this item is present in the sessionStorage, select our heading, and remove the class “animated” from it. 

if (window.sessionStorage.getItem('Heading')) {
  document.querySelector('#heading').classList.remove('animated')
}

From now on, the heading will remain in its normal position, and the animation will not play again.

Post last updated on May 22, 2023