How to seamlessly adjust the height from 0 to auto

Question

How to seamlessly adjust the height from 0 to auto

My goal is to smoothly transition from height: 0; to height: auto; and reveal the content inside a <div></div>. One effective method I've come across involves using the max-height property. Here's an example of how it can be implemented:

#menu #list {
  max-height: 0;
  transition: max-height 0.15s ease-out;
  overflow: hidden;
  background: #d5d5d5;
}

#menu:hover #list {
  max-height: 500px;
  transition: max-height 0.25s ease-in;
}

<div id="menu">
  <a>hover over me</a>
  <ul id="list">
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
  </ul>
</div>

While this method works well, there is a challenge when dealing with dynamic data retrieved from a database. The number of items within the list can vary greatly, making setting a fixed max-height impractical. Adjusting max-height based on the number of items through JavaScript would be complex and not ideal for responsive design.

I am seeking a solution that can accommodate both large and small amounts of items in a <ul> while maintaining smooth transitions. Ideally, a purely CSS-based solution would be perfect, but I am open to incorporating JavaScript if necessary.

javascript html css

Answer 1

Answer №1

To achieve this effect, JavaScript can be utilized.

Specify the transition to target the height property. Upon hovering (using mouseenter), set the height value based on the content's scrollHeight.

Once the transition is finished, adjust the height to auto so that any future changes in height are automatically accommodated (e.g., adding another item while the list is still open). This results in a smooth transition between 0 and auto.

On mouseleave, reset the height back to the scrollHeight (as transitioning from auto isn't feasible), allow the browser to repaint (using setTimeout with a 0 delay or requestAnimationFrame), and then return to 0.

const list = document.getElementById('list');
const trigger = document.getElementById('trigger');
let timeout;

trigger.addEventListener('mouseenter', () => {
  list.style.height = `${list.scrollHeight}px`;
  // Remove the hardcoded height at the end of the transition
  // so that further changes to the height will be automatically
  // reflected
  clearTimeout(timeout);
  timeout = setTimeout(() => list.style.height = 'auto', 150); // Should match the transition delay
});

trigger.addEventListener('mouseleave', () => {
  clearTimeout(timeout);
  list.style.height = `${list.scrollHeight}px`; // Set it to the height again
  timeout = setTimeout(() => list.style.height = 0, 0); // Wait for paint
});

#list {
  height: 0;
  transition: height 0.15s ease-out;
  overflow: hidden;
  background: #d5d5d5;
}

<div id="menu">
  <a id="trigger">hover over me</a>
  <ul id="list">
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
  </ul>
</div>

Answer 2

To achieve this effect, JavaScript can be utilized.

Specify the transition to target the height property. Upon hovering (using mouseenter), set the height value based on the content's scrollHeight.

Once the transition is finished, adjust the height to auto so that any future changes in height are automatically accommodated (e.g., adding another item while the list is still open). This results in a smooth transition between 0 and auto.

On mouseleave, reset the height back to the scrollHeight (as transitioning from auto isn't feasible), allow the browser to repaint (using setTimeout with a 0 delay or requestAnimationFrame), and then return to 0.

const list = document.getElementById('list');
const trigger = document.getElementById('trigger');
let timeout;

trigger.addEventListener('mouseenter', () => {
  list.style.height = `${list.scrollHeight}px`;
  // Remove the hardcoded height at the end of the transition
  // so that further changes to the height will be automatically
  // reflected
  clearTimeout(timeout);
  timeout = setTimeout(() => list.style.height = 'auto', 150); // Should match the transition delay
});

trigger.addEventListener('mouseleave', () => {
  clearTimeout(timeout);
  list.style.height = `${list.scrollHeight}px`; // Set it to the height again
  timeout = setTimeout(() => list.style.height = 0, 0); // Wait for paint
});

#list {
  height: 0;
  transition: height 0.15s ease-out;
  overflow: hidden;
  background: #d5d5d5;
}

<div id="menu">
  <a id="trigger">hover over me</a>
  <ul id="list">
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
  </ul>
</div>

Answer 3

Answer №2

To achieve this effect, you can utilize JavaScript. By using the childElementCount property, you can determine the number of li elements within a specific ul element and dynamically adjust the maxHeight accordingly.

let ul = document.querySelector("#list")

document.querySelector("#menu").onmouseover = function (){
  ul.style.maxHeight = 100*ul.childElementCount + "px";
};

document.querySelector("#menu").onmouseleave = function (){
  ul.style.maxHeight = 0;
};

#menu #list {
  max-height: 0;
  transition: max-height 0.15s ease-out;
  overflow: hidden;
  background: #d5d5d5;
}

#menu:hover #list {
  transition: max-height 0.25s ease-in;
}

<div id="menu">
  <a>hover over me</a>
  <ul id="list">
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
  </ul>
</div>

Answer 4

To achieve this effect, you can utilize JavaScript. By using the childElementCount property, you can determine the number of li elements within a specific ul element and dynamically adjust the maxHeight accordingly.

let ul = document.querySelector("#list")

document.querySelector("#menu").onmouseover = function (){
  ul.style.maxHeight = 100*ul.childElementCount + "px";
};

document.querySelector("#menu").onmouseleave = function (){
  ul.style.maxHeight = 0;
};

#menu #list {
  max-height: 0;
  transition: max-height 0.15s ease-out;
  overflow: hidden;
  background: #d5d5d5;
}

#menu:hover #list {
  transition: max-height 0.25s ease-in;
}

<div id="menu">
  <a>hover over me</a>
  <ul id="list">
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
    <li>item</li>
  </ul>
</div>

How to seamlessly adjust the height from 0 to auto

Answer №1

Answer №2

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