comparison

by Ascalon

HTML

Old button: does <button class="oldcol">this</button> work?
<div class="oldcon"><p>Yes!<p/></div>

<hr>

<div class=container>

    New button: does <button class="newcol">this</button><span class=newcon>Quite good</span> work?<br>
    New button fadein: does <button class="newcol">this</button><span class="newcon fadein">Quite good</span> work?<br>

</div>

CSS

.oldcol {
  cursor: help;
  border: none;
  outline: none;
  background: none;
  padding: 0;
  font-size: 1em;
  color: green;
  border-bottom: 1px dashed;
  transition: .3s;
}

.oldcon {
  padding: 0 18px;
  margin: 3px 0;
  max-height: 0;
  overflow: hidden;
  transition: .3s ease-out;
  background-color: #f1f1f1;
  box-shadow: 5px 5px 10px 3px inset rgba(0,0,0,0.60);
}

.container {
  position: relative;
  margin: 0em;
}
.newcon {
  display: none;
  padding: 0.6em;
  margin: 0.5em;
  background: #f1f1f1;
  box-shadow: 5px 5px 10px 3px inset rgba(0,0,0,0.60);
}
.newcol {
  cursor: help;
  border: none;
  outline: none;
  background: none;
  padding: 0;
  font-size: 1em;
  color: green;
  border-bottom: 1px dashed;
  transition: .3s ease-out;
}
.newcol:focus {
  pointer-events: none;
  margin-bottom: 3em;
}
.newcol:focus + .newcon
{
  display: block;
  margin-top: -2.5em;
  position: absolute;
  left: 0;
  right: 0;
}

.fadein {
  animation: fadein 1s;
}
@keyframes fadein {
  from {opacity:0}
  to {opacity:1}
}

JavaScript

var coll = document.getElementsByClassName("oldcol");
var i;

for (i = 0; i < coll.length; i++) {
  coll[i].addEventListener("click", function() {
    this.classList.toggle("active");
    var content = this.nextElementSibling;
    if (content.style.maxHeight) {
      content.style.maxHeight = null;
    } else {
      content.style.maxHeight = content.scrollHeight + "px";
    }
  });
}