Activate CSS3 keyframe animation when the content scrolls into view

Problem

I have been trying to figure out how to have animations occur when it is scrolled into view but with little to no luck. I found a JQuery plugin "Waypoints" but I lack the skills to utilize it. I am trying to use CSS3 keyframes that animate when they are scrolled into view. I made a breakthrough and am close to what I want to accomplish but it isn't quite where I want it. I have a class named "bounceinright" that makes the item bounce in to the right of the screen. Here is the CSS for that:

@-webkit-keyframes bounceinright {
0% {
    opacity: 0;
    -webkit-transform: translateX(2000px);
}

60% {
    opacity: 1;
    -webkit-transform: translateX(-30px);
}

80% {
    -webkit-transform: translateX(10px);
}

100% {
    -webkit-transform: translateX(0);
}
}

@-moz-keyframes bounceinright {
0% {
    opacity: 0;
    -moz-transform: translateX(2000px);
}

60% {
    opacity: 1;
    -moz-transform: translateX(-30px);
}

80% {
    -moz-transform: translateX(10px);
}

100% {
    -moz-transform: translateX(0);
}
}

@-o-keyframes bounceinright {
-o-transform: translateX(2000px);
}

60% {
opacity: 1;
-o-transform: translateX(-30px);
}

80% {
-o-transform: translateX(10px);
}

100% {
-o-transform: translateX(0);
}   
}

@keyframes bounceinright {
0% {
    opacity: 0;
    transform: translateX(2000px);
}

60% {
    opacity: 1;
    transform: translateX(-30px);
}

80% {
    transform: translateX(10px);
}

100% {
    transform: translateX(0);
}
 }

.bounceinright {
display: none;
}

.bounceinright.start {
-webkit-animation: bounceinright 1s ease-out forwards;
-moz-animation: bounceinright 1s ease-out forwards;
-ms-animation: bounceinright 1s ease-out forwards;
-o-animation: bounceinright 1s ease-out forwards;
animation: eigbounceinrighthty 1s ease-out forwards;
display: block;
}

and then I have a little JQuery snippet that will trigger the animation with the class "start" when it is scrolled to.

 ////////////////////////////////
 //scroll events
 ////////////////////////////////       
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 = $('.row .wpb_content_element');

    // 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();
});

my problem though is that when one item with "bounceinright" is scrolled to, it triggers ALL of the items with the same class. I was wondering if there was a way to have them trigger individually but with the same class. Any help would be appreciated.

Thank you!

Problem courtesy of: simpleminded

Solution

Change your checkAnimation() to

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

    $elem.each(function(){
        var $singleElement = $(this);
        // If the animation has already been started
        if ($singleElement.hasClass('start')) return;

        if (isElementInViewport($singleElement)) {
            // Start the animation
            $singleElement.addClass('start');
        }
    });
}
Solution courtesy of: Gaby aka G. Petrioli

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