CodePen Embed - accordion use TweenMax

<section class="content_accordion section">
				<header class="section_index">
					<h2>accordion</h2>
				</header>
				<div class="section_content">
					<dl class="content_accordion_child" data-accordion="open">
						<dt class="content_accordion_child_index">
							見出し1
							<span class="content_accordion_child_indexCap close">close</span>
							<span class="content_accordion_child_indexCap open">open</span>													
						</dt>
						<dd class="content_accordion_child_content" >
							 <p>アコーディオン1のコンテンツアコーディオン1のコンテンツ<br>アコーディオン1のコンテンツ</p>
						</dd>
					</dl>
					<dl class="content_accordion_child close" data-accordion="close">
						<dt class="content_accordion_child_index">
							見出し2
							<span class="content_accordion_child_indexCap close">close</span>
							<span class="content_accordion_child_indexCap open">open</span>													
						</dt>
						<dd class="content_accordion_child_content" >
							 <p>アコーディオン2のコンテンツアコーディオン2のコンテンツ<br>アコーディオン2のコンテンツ</p>
						</dd>
					</dl>
					<dl class="content_accordion_child close" data-accordion="close">
						<dt class="content_accordion_child_index">
							見出し3
							<span class="content_accordion_child_indexCap close">close</span>
							<span class="content_accordion_child_indexCap open">open</span>							
						</dt>
						<dd class="content_accordion_child_content" >
							 <p>アコーディオン3のコンテンツアコーディオン3のコンテンツ<br>アコーディオン3のコンテンツ</p>
						</dd>
					</dl>
				</div>
			</section>

	<script type="text/javascript" src="http://satohmsys.info/files/demo/tweenmax/site/js/tweenmax/minified/TweenMax.min.js"></script>

@import url(https://fonts.googleapis.com/css?family=Pacifico);
body, html {
  padding: 0;
  margin: 0;
}

html {
  position: relative;
  border-top: solid 5px #121212;
  line-height: 1.6;
}

img {
  line-height: 1;
  max-width: 100%;
  height: auto;
  outline: 0;
}

ul {
  margin: 0;
  padding: 0;
}

.content_accordion .section_index {
  display: table;
  text-align: center;
  white-space: nowrap;
}
.content_accordion .section_index:after, .content_accordion .section_index:before {
  content: '';
  display: table-cell;
  width: 50%;
  background: linear-gradient(rgba(0, 0, 0, 0) 50%, currentColor 50%, currentColor calc(50% + 1px), rgba(0, 0, 0, 0) calc(50% + 1px));
  background-clip: padding-box;
}
.content_accordion .section_index:after {
  border-left: 1em solid transparent;
}
.content_accordion .section_index:before {
  border-right: 1em solid transparent;
}
.content_accordion .section_index {
  font-size: 1em;
  font-weight: normal;
}
.content_accordion .section_content {
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-justify-content: space-around;
      -ms-flex-pack: distribute;
          justify-content: space-around;
  -webkit-align-content: start;
      -ms-flex-line-pack: start;
          align-content: start;
}
.content_accordion_child {
  -webkit-flex-basis: 30%;
      -ms-flex-preferred-size: 30%;
          flex-basis: 30%;
}
.content_accordion_child.close .content_accordion_child_content {
  height: 0;
  display: none;
}
.content_accordion_child_index, .content_accordion_child_content p {
  padding: 1em;
}
.content_accordion_child_index {
  line-height: 1;
  position: relative;
  text-align: center;
  background-color: #eee;
}
.content_accordion_child_indexCap {
  height: 1em;
  margin: auto;
  padding: 0.5em;
  cursor: pointer;
  transition: all 0.5s;
  opacity: 1;
  position: absolute;
  top: 0;
  right: 5px;
  bottom: 0;
  font-size: 0.6em;
  color: #fff;
  border-radius: 3px;
  background-color: #999;
}
.content_accordion_child_indexCap.open {
  background-color: #666;
}
.content_accordion_child_content {
  border: solid 1px #eee;
  margin-left: 0;
}
.content_accordion [data-accordion="open"] .open {
  opacity: 0;
}
.content_accordion [data-accordion="open"] .close {
  opacity: 1;
}
.content_accordion [data-accordion="close"] .open {
  opacity: 1;
}
.content_accordion [data-accordion="close"] .close {
  opacity: 0;
}
@media screen and (max-width: 600px) {
  .content_accordion .section_content {
    -webkit-flex-direction: column;
        -ms-flex-direction: column;
            flex-direction: column;
  }
}

var getByClass = function( cls, num ){
	if( typeof num == "number" ){
		classCollection = document.getElementsByClassName( cls )[num];
	} else {
		classCollection = document.getElementsByClassName( cls );
		classCollection.length == 1 ? classCollection = classCollection[0] : '';

	}
	return classCollection;
};

$accordion = getByClass( 'content_accordion_child' ),
$accordion_tab = getByClass( 'content_accordion_child_index' ),
$TimelineMax = new TimelineMax();


/**
* アコーディオン
*/

Array.prototype.forEach.call( $accordion, function( e, index ){
	var $index =  e.getElementsByClassName( 'content_accordion_child_index' );

	$index[0].addEventListener( 'click', function( e ){
		var $text = e.target;
		
		if( /indexCap/.test( $text.className ) ){
			$parent = $text.parentNode,
			$dd = $parent.nextElementSibling,
			$dtHeight = $parent.clientHeight;
		} else {
			$dd = $text.nextElementSibling,
			$dtHeight = $text.clientHeight;
		}
		$dl = $dd.parentNode,
		$status = $dl.getAttribute('data-accordion');

		//open時＝閉じる
		if( $status == 'open' ){		
			$TimelineMax.fromTo( $dd, 0.5, {
				overflow: 'hidden',
			},
			{
				height: 0,
				display: 'none',
				ease:Back.easeIn,
				onComplete: function( ){
					$dl.setAttribute( 'data-accordion', 'close' );
				}
			});
		} else {
			//close時＝開く
			
			$TimelineMax.fromTo( $dd, 1, {
				display: 'block',
				overflow: 'hidden'
			},
			{
				height: '80%',
				delay: 0.5,
				ease:Bounce.easeOut,
				onComplete: function(){
					$dl.setAttribute( 'data-accordion', 'open' );
				}
			});		
		}
		
	} );
} );

This Pen is owned by satoh masayasu on CodePen.

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