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                <button onclick="runAnimations()">Animate</button>
  <li><span class="countup">45</span></li>
  <li><span class="countup">110</span></li>
  <li><span class="countup">53210</span></li>




                // How long you want the animation to take, in ms
const animationDuration = 2000;
// Calculate how long each ‘frame’ should last if we want to update the animation 60 times per second
const frameDuration = 1000 / 60;
// Use that to calculate how many frames we need to complete the animation
const totalFrames = Math.round( animationDuration / frameDuration );
// An ease-out function that slows the count as it progresses
const easeOutQuad = t => t * ( 2 - t );

// The animation function, which takes an Element
const animateCountUp = el => {
	let frame = 0;
	const countTo = parseInt( el.innerHTML, 10 );
	// Start the animation running 60 times per second
	const counter = setInterval( () => {
		// Calculate our progress as a value between 0 and 1
		// Pass that value to our easing function to get our
		// progress on a curve
		const progress = easeOutQuad( frame / totalFrames );
		// Use the progress value to calculate the current count
		const currentCount = Math.round( countTo * progress );

		// If the current count has changed, update the element
		if ( parseInt( el.innerHTML, 10 ) !== currentCount ) {
			el.innerHTML = currentCount;

		// If we’ve reached our last frame, stop the animation
		if ( frame === totalFrames ) {
			clearInterval( counter );
	}, frameDuration );

// Run the animation on all elements with a class of ‘countup’
const runAnimations = () => {
	const countupEls = document.querySelectorAll( '.countup' );
	countupEls.forEach( animateCountUp );