Battery Manager API

2 min readOct 17, 2018

BatteryManager API

This API lets us keep track of the system’s battery charge level. This API is obsolete. It works only for some browsers.

First, we need to know if this API is available on the clients’ browser.

‘BatteryManager’ in window

This will return true only if BatteryManager is available on the clients’ browser.

Now let’s check its properties:

BatteryManager.charging
This will return a boolean value indicating whether or not the battery is currently being charged
BatteryManager.chargingTime
A number representing the remaining time in seconds until the battery is fully charged, or 0 if the battery is already fully charged.
BatteryManager.dischargingTime
A number representing the remaining time in seconds until the battery is completely discharged or Infinity if the battery is currently being charged.
BatteryManager.level
This will return a number in the range of 0.0 to 1.0 which represents the battery charge level.

Then, event handlers:

BatteryManager.addEventListener
A handler for the chargingchange event. This vent is sent when the battery charging state is updated
BatteryManager.onchargingtimechange
A handler for the chargingtimechange event. This event is sent when the battery charging time is updated.
BatteryManager.ondischargingtimechange
A handler for the dischargingtimechange event. This event is sent when the battery discharging time is updated.
BatteryManager.onlevelchange
A handler for the levelchange event. This event is sent when the battery level is updated.

Now let’s try it out…

Consider, we need to get the battery level of the device.

It’s clear from the example, the method getBattery() of navigator will return a Promise of proto of BatteryManager.

For further reference of a particular battery state, you can get the promise into a variable and then collect the Promise values.