Get navigator's battery data (current percentage, power source, usage time remaining and time to fully charge)

readBattery.js

(function() {
  let battery;

  function toTime(sec) {
    sec = parseInt(sec, 10)

    let hours = Math.floor(sec / 3600)
    let minutes = Math.floor((sec - (hours * 3600)) / 60)
    let seconds = sec - (hours * 3600) - (minutes * 60)

    if (hours < 10) hours = '0' + hours
    if (minutes < 10) minutes = '0' + minutes
    if (seconds < 10) seconds = '0' + seconds

    return `${hours}:${minutes}`
  }

  function readBattery(b) {
    battery = b || battery

    const percentage = parseFloat((battery.level * 100).toFixed(2)) + '%'
    let fully
    let remaining

    if (battery.charging && battery.chargingTime === Infinity) fully = 'Calculating...'
    else if (battery.chargingTime !== Infinity) fully = toTime(battery.chargingTime)
    else fully = '---'

    if (!battery.charging && battery.dischargingTime === Infinity) remaining = 'Calculating...'
    else if (battery.dischargingTime !== Infinity) remaining = toTime(battery.dischargingTime)
    else remaining = '---'

   
    const status = {
      percentage,
      status: battery.charging ? 'Adapter' : 'Battery',
      time: fully,
      remaining
    }
    
    console.table(status)
    return status
  }

  if (navigator.battery) readBattery(navigator.battery)
  else if (navigator.getBattery) navigator.getBattery().then(readBattery)
  else console.warn('Battery API is not supported in your browser; please use Chrome')

  window.onload = () => {
    battery.addEventListener('chargingchange', () => readBattery())
    battery.addEventListener("levelchange", () => readBattery())
  }
}())