Trigger CSS Animations in JavaScript

Question

I don't know how to use JQuery, so I need a method which could trigger an animation using JavaScript only.

I need to call/trigger CSS Animation when the user scrolls the page.

function start() {    document.getElementById('logo').style.animation = "anim 2s 2s forward";    document.getElementById('earthlogo').style.animation = "anim2 2s 2s forward";  }

* {    margin: 0px;  }    #logo {    position: fixed;    top: 200px;    height: 200px;    width: 1000px;    left: 5%;    z-index: 4;    opacity: 0.8;  }    #earthlogo {    position: fixed;    top: 200px;    height: 120px;    align-self: center;    left: 5%;    margin-left: 870px;    margin-top: 60px;    z-index: 4;    opacity: 0.9;  }    @keyframes anim {    50% {      filter: blur(10px);      transform: rotate(-15deg);      box-shadow: 0px 0px 10px 3px;    }    100% {      height: 100px;      width: 500px;      left: 10px;      top: 10px;      box-shadow: 0px 0px 15px 5px rgba(0, 0, 0, 0.7);      background-color: rgba(0, 0, 1, 0.3);      opacity: 0.7;    }  }    @keyframes anim2 {    50% {      filter: blur(40px);      transform: rotate(-15deg);    }    100% {      height: 60px;      width: 60px;      left: 10px;      top: 10px;      margin-left: 435px;      margin-top: 30px;      opacity: 0.8;    }  }    #backstar {    position: fixed;    width: 100%;    z-index: 1;  }    #earth {    position: absolute;    width: 100%;    z-index: 2;    top: 300px;  }

<img src="logo.png" id="logo" onclick="start();">  <img src="earthlogo.gif" id="earthlogo" onscroll="start();">  <img src="earth.png" id="earth">  <img src="stars.jpg" id="backstar">

Answer 1

The simplest method to trigger CSS animations is by adding or removing a class - how to do this with pure Javascript you can read here:

How do I add a class to a given element?

If you DO use jQuery (which should really be easy to learn in basic usage) you do it simply with addClass / removeClass.

All you have to do then is set a transition to a given element like this:

.el {     width:10px;     transition: all 2s; } 

And then change its state if the element has a class:

.el.addedclass {     width:20px; } 

Note: This example was with transition. But for animations its the same: Just add the animation on the element which has a class on it.

There is a similar question here: Trigger a CSS keyframe animation via scroll

Answer 2

This is how you can use vanilla JavaScript to change/trigger an animation associated with an HTML element.

First, you define your animations in CSS.

@keyframes spin1 { 100% { transform:rotate(360deg); } } @keyframes spin2 { 100% { transform:rotate(-360deg); } } @keyframes idle { 100% {} } 

Then you use javascript to switch between animations.

document.getElementById('yourElement').style.animation="spin2 4s linear infinite"; 

Note: 'yourElement' is the target HTML element id that you wish to animate.

For example: <div id="yourElement"> ... </div> or <table id='yourElement'>...</table>