No CSS transition for 'height: fit-content'

Question

I use transition: height 500ms to add an animation to an element that slides open via button from height: 0 to height: 100px and vice versa.

Since the element's content is added dynamically and I don't know it's size I would like to switch to height: fit-content instead. This way the element would have always the right size to show it's content.

Sadly this disables the animation.

How can I get the animation together with a div element which size fits its content?

Following snippet shows the behavior:

document.querySelector('button')
  .addEventListener(
    'click',
    () => document.querySelectorAll('div')
      .forEach(div => div.classList.toggle('closed')));

div {
  background-color: lightblue;
  border: 1px solid black;
  overflow: hidden;
  transition: height 500ms;
}

div.closed {
  height: 0 !important;
}

div.div1 {
  height: 100px;
}

div.div2 {
  height: fit-content;
}

<button type="button">toggle</button>

<h1>'height: 100px' => 'height: 0'</h1>
<div class="div1">
some text<br />
even more text<br />
so much text
</div>

<br>

<h1>'height: fit-content' => 'height: 0'</h1>
<div class="div2">
some text<br />
even more text<br />
so much text
</div>

Answer 1

one possible solution, though not perfect, is to animate font-size instead of height.

another solution might be to animate max-height instead of height. you can use max-height say 300px or 500px. but if you require more than that, it won't look good.

here I'm animating font-size.

Hope that helps. Thanks.

document.querySelector('button')
  .addEventListener(
    'click',
    () => document.querySelectorAll('div')
      .forEach(div => div.classList.toggle('closed')));

div {
  background-color: lightblue;
  border: 1px solid black;
  overflow: hidden;
  transition: font-size 500ms;
}

div.closed {
  font-size: 0 !important;
}

div.div1 {
  font-size: 14px;
}

div.div2 {
  font-size: 14px;
}

<button type="button">toggle</button>

<h1>'height: 100px' => 'height: 0'</h1>
<div class="div1">
some text<br />
even more text<br />
so much text
</div>

<br>

<h1>'height: fit-content' => 'height: 0'</h1>
<div class="div2">
some text<br />
even more text<br />
so much text
</div>

Answer 2

As Mishel stated another solution is to use max-height. Here is a working example of that solution.

The key is to approximate your max-height when it is fully expanded, then the transitions will be smooth.

Hope this helps.

https://www.w3schools.com/css/css3_transitions.asp

document.querySelector('button')
  .addEventListener(
    'click',
    () => document.querySelectorAll('div')
      .forEach(div => div.classList.toggle('closed')));

div {
  background-color: lightblue;
  border: 1px solid black;
  overflow-y: hidden;
	max-height: 75px; /* approximate max height */
	transition-property: all;
	transition-duration: .5s;
	transition-timing-function: cubic-bezier(1, 1, 1, 1);
}
div.closed {
   max-height: 0;
}

<button type="button">toggle</button>

<h1>'height: 100px' => 'height: 0'</h1>
<div class="div1">
some text<br />
even more text<br />
so much text
</div>

<br>

<h1>'height: fit-content' => 'height: 0'</h1>
<div class="div2">
some text<br />
even more text<br />
so much text
</div>