JavaScript Media Queries: Beyond Window Resize
What springs to mind when you think of media queries? Likely, CSS rules like this:
body { background-color: plum; } @media (min-width: 768px) { body { background-color: tomato; } }
CSS media queries are fundamental to responsive design, applying styles based on viewport size, device type, preferences (color scheme, motion), and more. But JavaScript also offers media query capabilities, often valuable for creating responsive plugins or dynamically adjusting elements based on screen conditions.
Unlike CSS, JavaScript's media query handling differs. The core concept remains the same: match conditions and apply actions.
Using matchMedia()
The matchMedia()
method determines if a media query matches the current document state. Despite being in the CSS Object Model View Module Working Draft, browser support is excellent.
The usage mirrors CSS: pass a media query string to matchMedia()
and check the .matches
property.
// Define the query const mediaQuery = window.matchMedia('(min-width: 768px)');
matchMedia()
returns a MediaQueryList
object. Its .matches
property (read-only Boolean) indicates whether the document matches the query.
// Create a media condition for viewports at least 768px wide const mediaQuery = window.matchMedia('(min-width: 768px)'); // Check if the media query matches if (mediaQuery.matches) { // Trigger an action alert('Media Query Matched!'); }
This handles single checks. For continuous monitoring, we need event listeners.
Listening for Changes
MediaQueryList
provides addListener()
(and removeListener()
) to register a callback function (.onchange
event) triggered when the media query status changes. This allows responsive actions to updated conditions.
// Create a condition for viewports at least 768px wide const mediaQuery = window.matchMedia('(min-width: 768px)'); function handleTabletChange(e) { // Check if the media query matches if (e.matches) { // Perform an action console.log('Media Query Matched!'); } else { console.log('Media Query Unmatched!'); } } // Register event listener mediaQuery.addListener(handleTabletChange); // Initial check handleTabletChange(mediaQuery);
addListener()
doesn't fire immediately; you must manually call the handler with the MediaQueryList
object as an argument.
The "Old" Approach
For comparison, the older method uses a resize
event listener with window.innerWidth
or window.innerHeight
. This is less efficient and less versatile.
function checkMediaQuery() { // Check if window inner width is greater than 768px if (window.innerWidth > 768) { // Perform an action console.log('Media Query Matched!'); } } // Add a listener for window resize events window.addEventListener('resize', checkMediaQuery);
This is performance-intensive and limited to viewport size checks, unlike the more powerful matchMedia()
approach.
Conclusion
matchMedia()
and MediaQueryList
provide robust JavaScript media query handling, enabling both one-time and continuous checks, reacting to changes in various conditions beyond simple viewport size. The older resize
event listener remains functional but is less efficient and less feature-rich. The flexibility of matchMedia()
makes it the preferred method for modern responsive JavaScript development.
Here's an example demonstrating a capability unavailable with the old method: detecting landscape orientation. This is frequently used in HTML5 game development.
The above is the detailed content of Working with JavaScript Media Queries. For more information, please follow other related articles on the PHP Chinese website!

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