CODEWITHSUNDEEP
javascriptcsscss-animations
Mike Sav
Mike Sav

Reputation: 15291

Can I detect with JavaScript where we are percentage wise in a CSS Keyframe animation

I was thinking. I know I can detect when a CSS animation has started, finished or is repeated by listening for the animationstart, animationiteration, animationend events (obviously we are missing browser prefixes there), for example:

document.getElementById('identifier')
        .addEventListener("animationstart", function(){
          // do something...
        });

but I was wondering, is it possible to determine where we are are running a CSS animation, how for example with the following could I listen for when we are at 50% of the keyframe animation:

<!DOCTYPE html>
<html>
<head>
<style>
#animateDiv {
    width: 100px;
    height: 100px;
    background-color: red;
    position: relative;
    animation-name: example;
    animation-duration: 4s;
}

@keyframes example {
    0%   {background-color:red; left:0px; top:0px;}
    25%  {background-color:yellow; left:200px; top:0px;}
    50%  {background-color:blue; left:200px; top:200px;}
    75%  {background-color:green; left:0px; top:200px;}
    100% {background-color:red; left:0px; top:0px;}
}
</style>
</head>
<body>
<div id="animateDiv"></div>
<script>
// what do I do here? How do I listen for the 50% event of the keyframes?
document.getElementById('animateDiv').addEventListener('animation at 50%?', function() {
 console.log('got it');
})
</script>
</body>
</html>

Upvotes: 14

Views: 1880

Answers (3)

dfralan
dfralan

Reputation: 125

Like Vini said you have that chance, I make this for myself, you can change the "animation-play-state:" for any function you want.

//Animation pause at specific percentage, Example: pauseAnimationAt("myDiv",33,10)
    function pauseAnimationAt(l,p,d){
      percentage = p/d*1000;
      function pauseAnimation(){
        setTimeout(function(){ document.getElementById(l).style="animation-play-state: paused"; }, percentage);//l = Element ID, p = percentage when you wanna stopt animation, d = Duration of animation (Yes, you need to know that)
      }
      document.getElementById(l).addEventListener("animationstart", pauseAnimation());
    }

Upvotes: 0

Andy Fazulus
Andy Fazulus

Reputation: 45

Here's my take on it.

  1. Get the animation duration.
  2. Sprinkle some mathematics on it like Vini suggested.
  3. setTimeout()

Code:

const fn_runAtKeyframe = (DOMElement, keyframe, callback) => {
  const animationDuration = window.getComputedStyle(DOMElement).animationDuration;
  // animationDuration returns string, e.g. "5s" or "500ms", so need to parseInt()
  // if it is in seconds, change it to milliseconds
  let animationKeyframe
  if (animationDuration.replace(/[0-9]/g, '') === "s") {
    animationKeyframe = parseInt(animationDuration) * keyframe * 1000
  } else {
    animationKeyframe = parseInt(animationDuration) * keyframe
  }

  const doStuff = (e) => {
    setTimeout(() => {
      console.log(`Function "${callback.name}" will run at ${keyframe*100}% keyframe`)
      callback();
    }, animationKeyframe)
  }
  DOMElement.addEventListener("animationstart", doStuff); 
  // or use "animationiteration" depending on your usecase
}

Run it,

const animateDiv = document.querySelector("#animateDiv")
const keyframe = 0.5 // at 50% keyframe
const callback = () => {
  // do stuff here...
};
fn_runAtKeyframe(animateDiv, keyframe, callback)

Upvotes: 1

Vini Antichrist
Vini Antichrist

Reputation: 236

I don't know if you can get the exact keyframe from a CSS animation, but you can use some mathemathics to get it, like our mate Paulie_D suggested.

On your code, your animation is 4s length, so, the keyframe 50% of the annimation is after 2s:

//......
//when the animation starts....
setTimeout(function(){
      //Enter your stuff here
}, 2000); //2 seconds delay, considering your animation length = 4s;

You can also use (needs jQuery):

$("#animated_element").bind("half_animation", function(){
      //Ya stuff here
});
//.........
//When the animation starts...
setTimeout(function()
{
     $("#animated_element").trigger("half_animation");
}, 2000);

Or:

$("#animated_element").bind("half_animation", function(){
      once = 0;
      setTimeout(function()
      {
           //Ya stuff here....
      }, 2000)
});
//........
//When the animation starts
$("#animated_element").trigger("half_animation");

Upvotes: 5

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