JSFiddle - React, Tailwind, and code Playground

by Matt_Coughlin

HTML

<div class="content">
    <p>There are many variations of passages of Lorem Ipsum available, but the majority have suffered alteration in some form, by injected humour, or randomised words which don't look even slightly believable. If you are going to use a passage of Lorem Ipsum, you need to be sure there isn't anything embarrassing hidden in the middle of text. All the Lorem Ipsum generators on the Internet tend to repeat predefined chunks as necessary, making this the first true generator on the Internet. It uses a dictionary of over 200 Latin words, combined with a handful of model sentence structures, to generate Lorem Ipsum which looks reasonable. The generated Lorem Ipsum is therefore always free from repetition, injected humour, or non-characteristic words etc.</p>
    
    <p>There are many variations of passages of Lorem Ipsum available, but the majority have suffered alteration in some form, by injected humour, or randomised words which don't look even slightly believable. If you are going to use a passage of Lorem Ipsum, you need to be sure there isn't anything embarrassing hidden in the middle of text. All the Lorem Ipsum generators on the Internet tend to repeat predefined chunks as necessary, making this the first true generator on the Internet. It uses a dictionary of over 200 Latin words, combined with a handful of model sentence structures, to generate Lorem Ipsum which looks reasonable. The generated Lorem Ipsum is therefore always free from repetition, injected humour, or non-characteristic words etc.</p>
    
    <p>There are many variations of passages of Lorem Ipsum available, but the majority have suffered alteration in some form, by injected humour, or randomised words which don't look even slightly believable. If you are going to use a passage of Lorem Ipsum, you need to be sure there isn't anything embarrassing hidden in the middle of text. All the Lorem Ipsum generators on the Internet tend to repeat predefined chunks as necessary,...

CSS

.bar {
	height:20px;
	background:#cccccc;
	color:#f4f4f4;
	text-align:center;
	width:100%;
}

.level {
	height:20px;
	background:#aae0aa;
    width:80%;
}

.eighty.start {
	width: 0px;
	background: #aae0aa;
	-webkit-animation: eighty 2s ease-out forwards;
	   -moz-animation: eighty 2s ease-out forwards;
	    -ms-animation: eighty 2s ease-out forwards;
	     -o-animation: eighty 2s ease-out forwards;
	        animation: eighty 2s ease-out forwards;
}

@-moz-keyframes eighty {
    0% {
        width: 0px;
    }

    100% {
        width: 80%;
    }
}

@-webkit-keyframes eighty {
	0% {
	    width: 0px;
	}

	100% {
	    width: 80%;
	}
}

JavaScript

// Returns true if the specified element has been scrolled into the viewport.
function isElementInViewport(elem) {
    var $elem = $(elem);

    // Get the scroll position of the page.
    var scrollElem = ((navigator.userAgent.toLowerCase().indexOf('webkit') != -1) ? 'body' : 'html');
    var viewportTop = $(scrollElem).scrollTop();
    var viewportBottom = viewportTop + $(window).height();

    // Get the position of the element on the page.
    var elemTop = Math.round( $elem.offset().top );
    var elemBottom = elemTop + $elem.height();

    return ((elemTop < viewportBottom) && (elemBottom > viewportTop));
}

// Check if it's time to start the animation.
function checkAnimation() {
    var $elem = $('.bar .level');

    // If the animation has already been started
    if ($elem.hasClass('start')) return;

    if (isElementInViewport($elem)) {
        // Start the animation
        $elem.addClass('start');
    }
}

// Capture scroll events
$(window).scroll(function(){
    checkAnimation();
});