获得电池状态 navigator.getBattery()

navigator.getBattery().then(function(battery) {  

   console.log(battery)    

  /*

   charging: true

   chargingTime: 0

   dischargingTime: Infinity

   level: 1

   onchargingchange: null

   onchargingtimechange: null

   ondischargingtimechange: null

   onlevelchange: null

  */

   battery.addEventListener('chargingchange',function (){  
       alert(battery.charging?'在充电':'没在充电')//是否在充电  
   })

   battery.addEventListener('dischargingtimechange',function (info){
       console.log(info)//电池剩余时间改变时触发该事件
   })

   battery.addEventListener('levelchange',function (info){
       console.log(info)//在电池电量水平改变时触发
   })
 })