Ambient Light Events

The ambient light events are a handy way to make a web page or an application aware of any change in the light intensity. It allows them to react to such a change, for example by changing the color contrast of the User Interface (UI) or by changing the exposure necessary to take a picture.

Light Events

When the light sensor of a device detects a change in the light level, it notifies the browser of that change. When the browser gets such a notification, it fires a DeviceLightEvent event that provides information about the exact light intensity.

This event can be captured at the window object level by using the addEventListener method (using the devicelight event name) or by attaching an event handler to the window.ondevicelight property.

Once captured, the event object gives access to the light intensity expressed in lux through the DeviceLightEvent.value property.

Example

window.addEventListener('devicelight', function(event) {
  var html = document.getElementsByTagName('html')[0];

  if (event.value < 50) {
    html.classList.add('darklight');
    html.classList.remove('brightlight');
  } else {
    html.classList.add('brightlight');
    html.classList.remove('darklight');
  }
});

Specifications

Specification	Status	Comment
Ambient Light Sensor The definition of 'Ambient Light Events' in that specification.	Editor's Draft	Initial definition

Browser compatibility

[1] The devicelight event is implemented and preference enabled by default in Firefox Mobile for Android (15.0) and in Firefox OS (B2G). Starting with Gecko 22.0 (Firefox 22.0 / Thunderbird 22.0 / SeaMonkey 2.19) a desktop implementation for Mac OS X is also available. Support for Windows 7 is in progress (see bug 754199).

See also

• DeviceLightEvent
• devicelight