react-native/packages/rn-tester/js/examples/Performance/PerformanceApiExample.js

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 * @flow strict-local
 * @oncall react_native
 */

'use strict';

import * as React from 'react';
import {StyleSheet, View, Text, Button} from 'react-native';
import RNTesterPage from '../../components/RNTesterPage';

const {useState} = React;

function MemoryExample(): React.Node {
  // Memory API testing
  const [memoryInfo, setMemoryInfo] = useState<{
    jsHeapSizeLimit?: ?number,
    totalJSHeapSize?: ?number,
    usedJSHeapSize?: ?number,
  }>({});
  const onGetMemoryInfo = () => {
    // performance.memory is not included in bom.js yet.
    // Once we release the change in flow this can be removed.
    // $FlowFixMe[prop-missing]
    // $FlowFixMe[incompatible-call]
    setMemoryInfo(performance.memory);
  };
  return (
    <RNTesterPage noSpacer={true} noScroll={true} title="performance.memory">
      <View style={styles.container}>
        <Button onPress={onGetMemoryInfo} title="Click to update memory info" />
        <View>
          <Text>
            {`jsHeapSizeLimit: ${
              memoryInfo.jsHeapSizeLimit == null
                ? 'N/A'
                : memoryInfo.jsHeapSizeLimit
            } bytes`}
          </Text>
          <Text>
            {`totalJSHeapSize: ${
              memoryInfo.totalJSHeapSize == null
                ? 'N/A'
                : memoryInfo.totalJSHeapSize
            } bytes`}
          </Text>
          <Text>
            {`usedJSHeapSize: ${
              memoryInfo.usedJSHeapSize == null
                ? 'N/A'
                : memoryInfo.usedJSHeapSize
            } bytes`}
          </Text>
        </View>
      </View>
    </RNTesterPage>
  );
}

const styles = StyleSheet.create({
  container: {
    padding: 10,
  },
});

exports.title = 'Performance API Examples';
exports.category = 'Basic';
exports.description = 'Shows the performance API provided in React Native';
exports.examples = [
  {
    title: 'performance.memory',
    render: function (): React.Element<typeof MemoryExample> {
      return <MemoryExample />;
    },
  },
];