Indicates the current battery charge level as a value between
var level = battery.level
level is a number representing the system's battery charge level scaled to a value between 0.0 and 1.0. A value of 0 means the
battery, which is a
BatteryManager object, is empty and the system is about to be suspended. A value of 1.0 means the battery is full. A value of 1.0 is also returned if the implementation isn't able to determine the battery charge level or if the system is not battery-powered.
|Battery Status API||Working Draft||Last Call Working Draft.|
|Feature||Chrome||Firefox (Gecko)||Internet Explorer||Opera||Safari|
|Basic support||38||Supports the deprecated
10 (10) moz 
16 (16) (without prefix) 
|Not supported||25||Not supported|
|Feature||Android||Chrome for Android||Firefox Mobile (Gecko)||IE Mobile||Opera Mobile||Safari Mobile|
|Basic support||Not supported||39 ||Not supported||25 ||Not supported|
 Disabled by default in Firefox 10.0, but can be enabled setting the preference
true. Starting with Firefox 11.0,
mozBattery is enabled by default.
 The Battery API is currently supported on Android, Windows, and Linux with UPower installed. Support for MacOS is available starting with Gecko 18.0 (Firefox 18.0 / Thunderbird 18.0 / SeaMonkey 2.15).