MediaQueryList - Web APIs 编辑

A MediaQueryList object stores information on a media query applied to a document, with support for both immediate and event-driven matching against the state of the document. You can create a MediaQueryList by calling matchMedia() on the window object. The resulting object handles sending notifications to listeners when the media query state changes (i.e. when the media query test starts or stops evaluating to true).

This is very useful for adaptive design, since this makes it possible to observe a document to detect when its media queries change, instead of polling the values periodically, and allows you to programmatically make changes to a document based on media query status.

Properties

The MediaQueryList interface inherits properties from its parent interface, EventTarget.

matchesRead only

A Boolean that returns true if the document currently matches the media query list, or false if not.

mediaRead only

A DOMString representing a serialized media query.

Methods

The MediaQueryList interface inherits methods from its parent interface, EventTarget.

addListener()

Adds to the MediaQueryList a callback which is invoked whenever the media query status—whether or not the document matches the media queries in the list—changes. This method exists primarily for backward compatibility; if possible, you should instead use addEventListener() to watch for the change event.

removeListener()

Removes the specified listener callback from the callbacks to be invoked when the MediaQueryList changes media query status, which happens any time the document switches between matching and not matching the media queries listed in the MediaQueryList. This method has been kept for backward compatibility; if possible, you should generally use removeEventListener() to remove change notification callbacks (which should have previously been added using addEventListener()).

Events

The following events are delivered to MediaQueryList objects:

change

Sent to the MediaQueryList when the result of running the media query against the document changes. For example, if the media query is (min-width: 400px), the change event is fired any time the width of the document's viewport changes such that its width moves across the 400px boundary in either direction.
Also available using the onchange event handler property.

Examples

This simple example creates a MediaQueryList and then sets up a listener to detect when the media query status changes, running a custom function when it does to change the appearence of the page.

var para = document.querySelector('p');
var mql = window.matchMedia('(max-width: 600px)');

function screenTest(e) {
  if (e.matches) {
    /* the viewport is 600 pixels wide or less */
    para.textContent = 'This is a narrow screen — less than 600px wide.';
    document.body.style.backgroundColor = 'red';
  } else {
    /* the viewport is more than than 600 pixels wide */
    para.textContent = 'This is a wide screen — more than 600px wide.';
    document.body.style.backgroundColor = 'blue';
  }
}

mql.addEventListener('change', screenTest);

Note: You can find this example on GitHub (see the source code, and also see it running live).

You can find other examples on the individual property and method pages.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Media queries
• Using media queries from code
• window.matchMedia()
• MediaQueryListEvent
• The article Window.devicePixelRatio also has a useful example