HTML `details` Element Toggle State with JavaScript
To control the expansion or collapse state of the <details> element of HTML, the key is to manipulate its open attribute. 1. <details> is a native HTML element used to create a foldable content block. It is closed by default. Add the open attribute to expand by default. 2. Get the elements through JavaScript and set details.open = true to expand, details.open = false to collapse, use details.open = !details.open to switch states; 3. Common practice is to bind button click events to switch states; 4. Be careful not to judge the state with class or style, nor to set open in inline styles; 5. <details> has good compatibility in modern browsers, but old browsers may not support it; 6. Applicable scenarios include advanced form options, FAQ expansion answers, and hidden debugging information, etc. that require dynamic control of the display.
To put it directly, the key is to use JavaScript to control the expansion or collapse state of the <details></details> element of HTML. The key is to operate its open attribute.
What are <details></details> and open properties?
<details></details> is a native HTML element that creates foldable blocks of content. By default, it is closed, and the content inside will be displayed only after adding the open attribute. For example:
<details> <summary>Click to expand</summary> <p>Here is the details. </p> </details>
If the open attribute is added, the page will be expanded by default when loading:
<details open> <summary>Expand by default</summary> <p>This paragraph can be seen from the beginning. </p> </details>
How to switch the expansion state of <details> with JavaScript?
You can get the element through JS and then control its open attribute value. for example:
const details = document.querySelector('details'); // Expand details.open = true; // Collapse details.open = false; // Switch status details.open = !details.open;
A common practice is to bind click events to switch states, such as adding a button:
<button id="toggleDetails">Switch details</button>
<details id="myDetails">
<summary>More information</summary>
<p>More Instructions...</p>
</details>
<script>
document.getElementById('toggleDetails').addEventListener('click', function() {
const details = document.getElementById('myDetails');
details.open = !details.open;
});
</script> In this way, the user can control the expansion and collapse of <details></details> by clicking the button.
Frequently Asked Questions and Notes
- Don't use class or style to judge the status : Although you can add class to match the style changes,
openattribute that really controls the expansion/collapse. - It is invalid to write
openin inline style<details style="open: true"></details>it is necessary to use native attributes. - Compatibility is good, but don't expect old browsers to support : mainstream modern browsers support
<details></details>, but it will be ignored in IE or some older versions.
Suggestions for practical application scenarios
- "Advanced Options" collapse area in form
- Click to expand the answer in the FAQ page
- Hide debugging information, not displayed by default, click the button to expand to view
If you want certain content to be hidden by default, but allow users to expand actively, and want to use JS to dynamically control this behavior, <details></details> plus JS operate the open attribute is the simplest way.
Basically that's it.
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