useBattery

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React hook that tracks battery state

Example

Demo Code

import clsx from "clsx";
import useBattery, { type BatteryState } from "@/hooks/useBattery";

export default function UseBatteryExample() {
  const { isSupported, ...batteryState } = useBattery();

  if (!isSupported) {
    return <p>Battery API is not supported</p>;
  }

  const { fetched } = batteryState as { fetched: boolean };

  if (!fetched) {
    return <p>Battery API is not fetched yet</p>;
  }

  const { charging, level, chargingTime, dischargingTime } =
    batteryState as BatteryState;

  const getLevelColor = () => {
    if (level < 0.25) {
      return "bg-ctp-red";
    } else if (level < 0.5) {
      return "bg-ctp-yellow";
    } else {
      return "bg-ctp-green";
    }
  };

  const getBorderColor = () => {
    if (charging) {
      return "border-ctp-yellow";
    } else {
      return "border-ctp-surface2";
    }
  };

  return (
    <div className="flex items-center justify-start">
      <div className="w-48">
        <div className="relative my-1 flex w-1/2 rounded border-2 border-ctp-surface2 shadow">
          <div className="absolute z-10 ml-24 mt-2 flex h-6 rounded-r border-r-8 border-ctp-surface2"></div>
          <div
            className={clsx(
              "m-1 flex cursor-default items-center justify-center py-4 text-center text-xs font-bold leading-none",
              getLevelColor(),
            )}
            style={{ width: `${level * 100}%` }}
          >
            <div className="absolute left-0 mx-8 text-ctp-surface2">
              {level * 100}%
            </div>
          </div>
        </div>
      </div>
      <div className="text-ctp-text">
        Is charging: {charging ? "Yes" : "No"}
        <br />
        Charging time: {chargingTime}
        <br />
        Discharging time: {dischargingTime}
      </div>
    </div>
  );
}

Code

import { useEffect, useState } from "react";

export interface BatteryState {
  charging: boolean;
  chargingTime: number;
  dischargingTime: number;
  level: number;
}

interface BatteryManager extends Readonly<BatteryState>, EventTarget {
  onchargingchange: () => void;
  onchargingtimechange: () => void;
  ondischargingtimechange: () => void;
  onlevelchange: () => void;
}

interface NavigatorWithPossibleBattery extends Navigator {
  getBattery?: () => Promise<BatteryManager>;
}

type UseBatteryState =
  | { isSupported: false } // Battery API is not supported
  | { isSupported: true; fetched: false } // battery API supported but not fetched yet
  | (BatteryState & { isSupported: true; fetched: true }); // battery API supported and fetched

const nav: NavigatorWithPossibleBattery | undefined =
  typeof navigator !== "undefined" ? navigator : undefined;
const isBatteryApiSupported = nav && typeof nav.getBattery === "function";

function useBatteryMock(): UseBatteryState {
  return { isSupported: false };
}

/**
 * React hook that tracks battery state
 * @returns {UseBatteryState} battery state
 */
function useBattery(): UseBatteryState {
  const [state, setState] = useState<UseBatteryState>({
    isSupported: true,
    fetched: false,
  });

  useEffect(() => {
    let isMounted = true;
    let battery: BatteryManager | null = null;

    const handleChange = () => {
      if (!isMounted || !battery) {
        return;
      }
      const newState: UseBatteryState = {
        isSupported: true,
        fetched: true,
        level: battery.level,
        charging: battery.charging,
        dischargingTime: battery.dischargingTime,
        chargingTime: battery.chargingTime,
      };
      setState(newState);
    };

    nav!.getBattery!().then((bat: BatteryManager) => {
      if (!isMounted) {
        return;
      }
      battery = bat;
      window.addEventListener("chargingchange", handleChange);
      window.addEventListener("chargingtimechange", handleChange);
      window.addEventListener("dischargingtimechange", handleChange);
      window.addEventListener("levelchange", handleChange);
      handleChange();
    });

    return () => {
      isMounted = false;
      if (battery) {
        window.removeEventListener("chargingchange", handleChange);
        window.removeEventListener("chargingtimechange", handleChange);
        window.removeEventListener("dischargingtimechange", handleChange);
        window.removeEventListener("levelchange", handleChange);
      }
    };
  }, []);

  return state;
}

export default isBatteryApiSupported ? useBattery : useBatteryMock;