使用 React 必然会重复如下的代码：

import React from 'react';
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通过这段代码，我们从 react 的库中导入了 React，那这个 React 中到底包含哪些东西呢？

import ReactVersion from 'shared/ReactVersion';
import {REACT_CONCURRENT_MODE_TYPE,REACT_FRAGMENT_TYPE,REACT_PROFILER_TYPE,REACT_STRICT_MODE_TYPE,REACT_SUSPENSE_TYPE,
} from 'shared/ReactSymbols';import {Component, PureComponent} from './ReactBaseClasses';
import {createRef} from './ReactCreateRef';
import {forEach, map, count, toArray, only} from './ReactChildren';
import {createElement,createFactory,cloneElement,isValidElement,
} from './ReactElement';
import {createContext} from './ReactContext';
import {lazy} from './ReactLazy';
import forwardRef from './forwardRef';
import memo from './memo';
import {useCallback,useContext,useEffect,useImperativeHandle,useDebugValue,useLayoutEffect,useMemo,useReducer,useRef,useState,
} from './ReactHooks';
import {createElementWithValidation,createFactoryWithValidation,cloneElementWithValidation,
} from './ReactElementValidator';
import ReactSharedInternals from './ReactSharedInternals';
import {enableStableConcurrentModeAPIs} from 'shared/ReactFeatureFlags';const React = {Children: {map,forEach,count,toArray,only,},createRef,Component,PureComponent,createContext,forwardRef,lazy,memo,useCallback,useContext,useEffect,useImperativeHandle,useDebugValue,useLayoutEffect,useMemo,useReducer,useRef,useState,Fragment: REACT_FRAGMENT_TYPE,StrictMode: REACT_STRICT_MODE_TYPE,Suspense: REACT_SUSPENSE_TYPE,createElement: __DEV__ ? createElementWithValidation : createElement,cloneElement: __DEV__ ? cloneElementWithValidation : cloneElement,createFactory: __DEV__ ? createFactoryWithValidation : createFactory,isValidElement: isValidElement,version: ReactVersion,unstable_ConcurrentMode: REACT_CONCURRENT_MODE_TYPE,unstable_Profiler: REACT_PROFILER_TYPE,__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED: ReactSharedInternals,
};// Note: some APIs are added with feature flags.
// Make sure that stable builds for open source
// don't modify the React object to avoid deopts.
// Also let's not expose their names in stable builds.if (enableStableConcurrentModeAPIs) {React.ConcurrentMode = REACT_CONCURRENT_MODE_TYPE;React.Profiler = REACT_PROFILER_TYPE;React.unstable_ConcurrentMode = undefined;React.unstable_Profiler = undefined;
}export default React;
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结构

React Core，结构图如下

链接

• ReactBaseClasses
• ReactElement
• ReactHooks
• ReactContext
• ReactCreateRef
• forwardRef
• ReactLazy
• memo
• Children

React Element:

• createElement

• cloneElement

• createFactory

• isValidElement

• ReactElementValidator 用于开发环境

  • createElementWithValidation
  • cloneElementWithValidation
  • createFactoryWithValidation

React Symbol：

• Fragment
• StrictMode
• Suspense

其他：

• version