From 2d0fabf9accf2a3baa673e06e53eca345b62d52a Mon Sep 17 00:00:00 2001
From: streamich <streamich@gmail.com>
Date: Tue, 20 Aug 2019 20:17:55 +0200
Subject: [PATCH] =?UTF-8?q?feat:=20=F0=9F=8E=B8=20use=20only=20one=20useSt?=
 =?UTF-8?q?ate=20and=20one=20useEffect=20call?=
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---
 src/useBattery.ts | 87 ++++++++++++++++++-----------------------------
 1 file changed, 34 insertions(+), 53 deletions(-)

diff --git a/src/useBattery.ts b/src/useBattery.ts
index c2f6834f..3f675665 100644
--- a/src/useBattery.ts
+++ b/src/useBattery.ts
@@ -2,6 +2,8 @@ import * as React from 'react';
 import * as isEqual from 'react-fast-compare';
 import { off, on } from './util';
 
+const { useState, useEffect } = React;
+
 export interface BatteryState {
   charging: boolean;
   chargingTime: number;
@@ -33,68 +35,47 @@ function useBatteryMock(): UseBatteryState {
 }
 
 function useBattery(): UseBatteryState {
-  const [state, setState] = React.useState<UseBatteryState>({ isSupported: true, fetched: false });
-  const battery = React.useRef<BatteryManager | null>();
-  const isMounted = React.useRef(false);
+  const [state, setState] = useState<UseBatteryState>({ isSupported: true, fetched: false });
 
-  const handleChange = React.useCallback(() => {
-    if (!isMounted.current || !battery.current) {
-      return;
-    }
+  useEffect(() => {
+    let isMounted = true;
+    let battery: BatteryManager | null = null;
 
-    const newState: UseBatteryState = {
-      isSupported: true,
-      fetched: true,
-      level: battery.current.level,
-      charging: battery.current.charging,
-      dischargingTime: battery.current.dischargingTime,
-      chargingTime: battery.current.chargingTime,
+    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,
+      };
+      !isEqual(state, newState) && setState(newState);
     };
 
-    !isEqual(state, newState) && setState(newState);
-  }, [state, setState]);
-
-  const bindBatteryEvents = React.useCallback(() => {
-    if (!battery.current || !isMounted.current) {
-      return;
-    }
-
-    on(battery.current, 'chargingchange', handleChange);
-    on(battery.current, 'chargingtimechange', handleChange);
-    on(battery.current, 'dischargingtimechange', handleChange);
-    on(battery.current, 'levelchange', handleChange);
-  }, [handleChange]);
-  const unbindBatteryEvents = React.useCallback(() => {
-    if (!battery.current) {
-      return;
-    }
-
-    off(battery.current, 'chargingchange', handleChange);
-    off(battery.current, 'chargingtimechange', handleChange);
-    off(battery.current, 'dischargingtimechange', handleChange);
-    off(battery.current, 'levelchange', handleChange);
-  }, [handleChange]);
-
-  React.useEffect(() => {
-    bindBatteryEvents();
-    handleChange(); // this one is for case when update performed between unbind and bind, extremely rare, but better to handle
-
-    return unbindBatteryEvents;
-  }, [handleChange]);
-
-  React.useEffect(() => {
-    isMounted.current = true;
-
     (navigator as NavigatorWithPossibleBattery).getBattery!().then((bat: BatteryManager) => {
-      battery.current = bat;
-
-      bindBatteryEvents();
+      if (!isMounted) {
+        return;
+      }
+      battery = bat;
+      on(battery, 'chargingchange', handleChange);
+      on(battery, 'chargingtimechange', handleChange);
+      on(battery, 'dischargingtimechange', handleChange);
+      on(battery, 'levelchange', handleChange);
       handleChange();
     });
 
     return () => {
-      isMounted.current = false;
-      unbindBatteryEvents();
+      isMounted = false;
+      if (battery) {
+        off(battery, 'chargingchange', handleChange);
+        off(battery, 'chargingtimechange', handleChange);
+        off(battery, 'dischargingtimechange', handleChange);
+        off(battery, 'levelchange', handleChange);
+      }
     };
   }, []);