@react-native-webapis/battery-status

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THIS TOOL IS EXPERIMENTAL — USE WITH CAUTION

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Battery Status API for React Native.

[!NOTE]

This is purely a prototype for the React Native WebAPIs RFC. It currently does not implement the Battery Status API to spec, e.g. it's missing events and its properties are not updated live. Rather, its purpose is to show that it's possible to have a native module polyfill a web API, enabling direct use of previously web-only code in a React Native app.

Installation

yarn add @rnx-kit/polyfills --dev
yarn add @react-native-webapis/battery-status

or if you're using npm

npm add --save-dev @rnx-kit/polyfills
npm add @react-native-webapis/battery-status

Usage

diff --git a/packages/test-app/babel.config.js b/packages/test-app/babel.config.js
index 69ebd557..a012b7f5 100644
--- a/packages/test-app/babel.config.js
+++ b/packages/test-app/babel.config.js
@@ -13,6 +13,7 @@ module.exports = {
           { runtime: "automatic" },
         ],
         [require("@babel/plugin-transform-react-jsx-source")],
+        [require("@rnx-kit/polyfills")],
       ],
     },
   ],
diff --git a/packages/test-app/src/App.native.tsx b/packages/test-app/src/App.native.tsx
index 599634a9..a9b493ab 100644
--- a/packages/test-app/src/App.native.tsx
+++ b/packages/test-app/src/App.native.tsx
@@ -1,3 +1,5 @@
+// @react-native-webapis
+
 import { acquireTokenWithScopes } from "@rnx-kit/react-native-auth";
 // Both `internal` imports are used to verify that `metro-resolver-symlinks`
 // resolves them correctly when `experimental_retryResolvingFromDisk` is
@@ -7,7 +9,7 @@ import {
   getRemoteDebuggingAvailability,
 } from "internal";
 import { getHermesVersion } from "internal/hermes";
-import React, { useCallback, useMemo, useState } from "react";
+import React, { useCallback, useEffect, useMemo, useState } from "react";
 import type { LayoutChangeEvent } from "react-native";
 import {
   NativeModules,
@@ -186,6 +188,14 @@ function App({ concurrentRoot }: { concurrentRoot?: boolean }) {
     [setFabric]
   );

+  const [batteryLevel, setBatteryLevel] = useState(-1);
+  useEffect(() => {
+    // @ts-expect-error FIXME
+    navigator.getBattery().then((status) => {
+      setBatteryLevel(status.level);
+    });
+  }, []);
+
   return (
     <SafeAreaView style={styles.body}>
       <StatusBar barStyle={isDarkMode ? "light-content" : "dark-content"} />
@@ -195,6 +205,9 @@ function App({ concurrentRoot }: { concurrentRoot?: boolean }) {
         style={styles.body}
       >
         <Header />
+        <View style={styles.group}>
+          <Feature value={batteryLevel.toFixed(2)}>Battery Level</Feature>
+        </View>
         <View style={styles.group}>
           <Button onPress={startAcquireToken}>Acquire Token</Button>
         </View>