The more demanding our web apps become, the more power we draw from devices. On desktop, where we can be sure that the device is plugged into the mains, that's not a problem, but on a mobile device we need to know what the battery is doing and respond accordingly. Browser support ... At the time of writing the Battery API is only supported by Firefox (mobile and desktop). However, it doesn't require a vendor prefix to be supported. The reason I mention desktop is because this API can also be used with any laptop...