index.js — react Source File

Source Code

/**
 * 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.
 *
 * @flow
 */

import type {ReactContext} from 'shared/ReactTypes';
import * as React from 'react';
import {
  createContext,
  Component,
  forwardRef,
  Fragment,
  memo,
  useCallback,
  useDebugValue,
  useEffect,
  useReducer,
  useState,
} from 'react';

const initialData = {foo: 'FOO', bar: 'BAR'};

// $FlowFixMe[missing-local-annot]
function reducer(state, action: {type: string}) {
  switch (action.type) {
    case 'swap':
      return {foo: state.bar, bar: state.foo};
    default:
      throw new Error();
  }
}

type StatefulFunctionProps = {name: string};

function StatefulFunction({name}: StatefulFunctionProps) {
  const [count, updateCount] = useState(0);
  const debouncedCount = useDebounce(count, 1000);
  const handleUpdateCountClick = useCallback(
    () => updateCount(count + 1),
    [count],
  );

  const [data, dispatch] = useReducer(reducer, initialData);
  const handleUpdateReducerClick = useCallback(
    () => dispatch({type: 'swap'}),
    [],
  );

  return (
    <ul>
      <li>Name: {name}</li>
      <li>
        <button onClick={handleUpdateCountClick}>
          Debounced count: {debouncedCount}
        </button>
      </li>
// ... (116 more lines)