大家好，我是若川。我倾力持续组织了一年多每周大家一起学习200行左右的源码共读活动，感兴趣的可以点此扫码加我微信 ruochuan02 参与。另外，想学源码，极力推荐关注我写的专栏《学习源码整体架构系列》，目前是掘金关注人数（4.7k+人）第一的专栏，写有20余篇源码文章。
最近 React 出了 新文档 react.dev，新中文文档 zh-hans.react.dev。
现在用 react 开发离不开各种 hooks。学习各种 hooks 的工具库，有助于我们更好的使用和理解 hooks 。前端社区中有活跃的 ahooks。不过，这次我们来学习目前 36.2k star 的 react-use 库。
react-use 文档 是用 storybook 搭建的。
如果公司项目需要搭建组件库或者 hooks、工具库等，storybook 或许是不错的选择。
react-use 中文翻译仓库，最后更新是2年前，可能有点老。
看一个开源仓库，第一步一般是看 README.md 和 contributing.md 贡献文档。第二步的克隆下来。按照贡献指南文档，把项目跑起来。
贡献文档中有如下文档。
- 创建
src/useYourHookName.ts和stories/useYourHookName.story.tsx，然后运行yarn start。 - 创建
tests/useYourHookName.test.ts，运行yarn test:watch监听测试用例执行。 - 创建
docs/useYourHookName.md文档。 - 在
src/index.ts文件导出你写的hook，然后添加你的hook到REAMDE.md中。
我们可以得知具体要做什么，新增 hook 关联哪些文件。
# 推荐克隆我的仓库 git clone https://github.com/lxchuan12/react-use-analysis.git cd react-use-analysis/react-use # 也可以克隆官方项目 git clone https://github.com/streamich/react-use.git cd react-use yarn install yarn start克隆项目到本地，安装依赖完成后，执行 yarn start。
本地环境打开 useEffectOnce docs：http://localhost:6008/?path=/story/lifecycle-useeffectonce--docs
我们先挑选这个 useEffectOnce 简单的 hook 来分析。
// react-use/src/useEffectOnce.ts import { EffectCallback, useEffect } from 'react'; // 源码非常简单，不依赖任何参数的函数。 const useEffectOnce = (effect: EffectCallback) => { useEffect(effect, []); }; export default useEffectOnce;我们来看测试用例，直接使用测试用例调试 useEffectOnce 源码。
我之前写过相关文章。可以参考学习。 你可能不知道测试用例(Vitest)可以调试开源项目(Vue3) 源码
我装了 jest 和 jest runner vscode 插件，装完后测试用例中会直接显示 run、和 debug 按钮。还在装了 vitest、vitest runner vscode 插件，装完后测试用例中会直接显示 run(vitest)和 debug(vitest) 按钮。
如下图所示。
这个项目使用的是 jest。于是我点击最右侧的 debug。
// react-use/tests/useEffectOnce.test.ts import { renderHook } from '@testing-library/react-hooks'; import { useEffectOnce } from '../src'; // mock 函数 const mockEffectCleanup = jest.fn(); const mockEffectCallback = jest.fn().mockReturnValue(mockEffectCleanup); it('should run provided effect only once', () => { const { rerender } = renderHook(() => useEffectOnce(mockEffectCallback)); // 只调用一次 expect(mockEffectCallback).toHaveBeenCalledTimes(1); // 重新渲染时，只调用一次 rerender(); expect(mockEffectCallback).toHaveBeenCalledTimes(1); }); it('should run clean-up provided on unmount', () => { const { unmount } = renderHook(() => useEffectOnce(mockEffectCallback)); expect(mockEffectCleanup).not.toHaveBeenCalled(); unmount(); // 卸载时 执行一次 expect(mockEffectCleanup).toHaveBeenCalledTimes(1); });xxx.story.tsx 渲染组件，可以直接操作。Demo 和 docs。
// react-use/stories/useEffectOnce.story.tsx import { storiesOf } from '@storybook/react'; import * as React from 'react'; import { useEffectOnce } from '../src'; import ConsoleStory from './util/ConsoleStory'; import ShowDocs from './util/ShowDocs'; const Demo = () => { useEffectOnce(() => { console.log('Running effect once on mount'); return () => { console.log('Running clean-up of effect on unmount'); }; }); return <ConsoleStory />; }; storiesOf('Lifecycle/useEffectOnce', module) .add('Docs', () => <ShowDocs md={require('../docs/useEffectOnce.md')} />) .add('Demo', () => <Demo />);docs/useEffectOnce.md 省略，基本跟测试用例一样。可以说测试用例就是活文档。
接下来我们来看其他的 hooks 源码，限于篇幅，主要就讲述源码，不包含测试用例、文档、story。
TS 也不会过多描述。如果对TS不太熟悉，推荐学习这个《TypeScript 入门教程》。
我们先来看 Sensors 行为部分。
tracks whether user is being inactive. 跟踪用户是否处于非活动状态。
主要是：监听用户行为的事件（默认的 'mousemove', 'mousedown', 'resize', 'keydown', 'touchstart', 'wheel' ），指定时间内没有用户操作行为就是非活动状态。
import { useEffect, useState } from 'react'; // 防抖、节流 import { throttle } from 'throttle-debounce'; // 事件解绑和监听函数 import { off, on } from './misc/util'; // 监听默认事件 const defaultEvents = ['mousemove', 'mousedown', 'resize', 'keydown', 'touchstart', 'wheel']; const oneMinute = 60e3; const useIdle = ( ms: number = oneMinute, initialState: boolean = false, events: string[] = defaultEvents ): boolean => { const [state, setState] = useState<boolean>(initialState); useEffect(() => { let mounted = true; let timeout: any; let localState: boolean = state; const set = (newState: boolean) => { if (mounted) { localState = newState; setState(newState); } }; const onEvent = throttle(50, () => { if (localState) { set(false); } clearTimeout(timeout); timeout = setTimeout(() => set(true), ms); }); const onVisibility = () => { if (!document.hidden) { onEvent(); } }; for (let i = 0; i < events.length; i++) { on(window, events[i], onEvent); } on(document, 'visibilitychange', onVisibility); timeout = setTimeout(() => set(true), ms); return () => { mounted = false; // 销毁 解绑事件 for (let i = 0; i < events.length; i++) { off(window, events[i], onEvent); } off(document, 'visibilitychange', onVisibility); }; }, [ms, events]); return state; }; export default useIdle;我们接着来看，useLocation hook。
useLocation docs | useLocation demo
React sensor hook that tracks brower's location.
主要获取 window.location 等对象信息。
阮一峰老师的网道：history 阮一峰老师的网道：location
自定义事件 mdn 创建和触发 events
import { useEffect, useState } from 'react'; // 判断浏览器 import { isBrowser, off, on } from './misc/util'; const patchHistoryMethod = (method) => { const history = window.history; const original = history[method]; history[method] = function (state) { // 原先函数 const result = original.apply(this, arguments); // 自定义事件 new Event 、 dispatchEvent const event = new Event(method.toLowerCase()); (event as any).state = state; window.dispatchEvent(event); return result; }; }; if (isBrowser) { patchHistoryMethod('pushState'); patchHistoryMethod('replaceState'); } // 省略 LocationSensorState 类型 const useLocationServer = (): LocationSensorState => ({ trigger: 'load', length: 1, }); const buildState = (trigger: string) => { const { state, length } = window.history; const { hash, host, hostname, href, origin, pathname, port, protocol, search } = window.location; return { trigger, state, length, hash, host, hostname, href, origin, pathname, port, protocol, search, }; }; const useLocationBrowser = (): LocationSensorState => { const [state, setState] = useState(buildState('load')); useEffect(() => { const onPopstate = () => setState(buildState('popstate')); const onPushstate = () => setState(buildState('pushstate')); const onReplacestate = () => setState(buildState('replacestate')); on(window, 'popstate', onPopstate); on(window, 'pushstate', onPushstate); on(window, 'replacestate', onReplacestate); return () => { off(window, 'popstate', onPopstate); off(window, 'pushstate', onPushstate); off(window, 'replacestate', onReplacestate); }; }, []); return state; }; const hasEventConstructor = typeof Event === 'function'; export default isBrowser && hasEventConstructor ? useLocationBrowser : useLocationServer;接着我们继续来看 State 状态部分。
useFirstMountState docs | useFirstMountState demo
Returns true if component is just mounted (on first render) and false otherwise. 若组件刚刚加载（在第一次渲染时），则返回
true，否则返回false。
import { useRef } from 'react'; export function useFirstMountState(): boolean { const isFirst = useRef(true); if (isFirst.current) { isFirst.current = false; return true; } return isFirst.current; }usePrevious docs | usePrevious demo
React state hook that returns the previous state as described in the React hooks FAQ. 保留上一次的状态。
利用 useRef 的不变性。
import { useEffect, useRef } from 'react'; export default function usePrevious<T>(state: T): T | undefined { const ref = useRef<T>(); useEffect(() => { ref.current = state; }); return ref.current; }React state hook that tracks a Set.
new Set 的 hooks 用法。 useSet 可以用来列表展开、收起等其他场景。 返回 [set ,{add, remove, toggle, reset, has }]
import { useCallback, useMemo, useState } from 'react'; export interface StableActions<K> { add: (key: K) => void; remove: (key: K) => void; toggle: (key: K) => void; reset: () => void; } export interface Actions<K> extends StableActions<K> { has: (key: K) => boolean; } const useSet = <K>(initialSet = new Set<K>()): [Set<K>, Actions<K>] => { const [set, setSet] = useState(initialSet); const stableActions = useMemo<StableActions<K>>(() => { const add = (item: K) => setSet((prevSet) => new Set([...Array.from(prevSet), item])); const remove = (item: K) => setSet((prevSet) => new Set(Array.from(prevSet).filter((i) => i !== item))); const toggle = (item: K) => setSet((prevSet) => prevSet.has(item) ? new Set(Array.from(prevSet).filter((i) => i !== item)) : new Set([...Array.from(prevSet), item]) ); return { add, remove, toggle, reset: () => setSet(initialSet) }; }, [setSet]); const utils = { has: useCallback((item) => set.has(item), [set]), ...stableActions, } as Actions<K>; return [set, utils]; }; export default useSet;useToggle docs | useToggle demo
tracks state of a boolean. 跟踪布尔值的状态。 切换 false => true => false
import { Reducer, useReducer } from 'react'; const toggleReducer = (state: boolean, nextValue?: any) => typeof nextValue === 'boolean' ? nextValue : !state; const useToggle = (initialValue: boolean): [boolean, (nextValue?: any) => void] => { return useReducer<Reducer<boolean, any>>(toggleReducer, initialValue); }; export default useToggle;我们继续来看 Side-effects 副作用部分。
useMountedState 属于 lifecycle 模块，但这个 hook 在 useAsyncFn 中使用，所以放到这里讲述。
useMountedState docs | useMountedState demo
NOTE!: despite having State in its name this hook does not cause component re-render. This component designed to be used to avoid state updates on unmounted components.
注意！：尽管名称中有State，但该钩子不会导致组件重新呈现。此组件设计用于避免对未安装的组件进行状态更新。
Lifecycle hook providing ability to check component's mount state. Returns a function that will return true if component mounted and false otherwise. 生命周期挂钩提供了检查组件装载状态的能力。 返回一个函数，如果组件已安装，则返回true，否则返回false。
import { useCallback, useEffect, useRef } from 'react'; export default function useMountedState(): () => boolean { const mountedRef = useRef<boolean>(false); const get = useCallback(() => mountedRef.current, []); useEffect(() => { mountedRef.current = true; return () => { mountedRef.current = false; }; }, []); return get; }看了 useMountedState hook，我们继续看 useAsyncFn 函数源码。
主要函数传入 Promise 函数 fn，然后执行函数 fn.then()。 返回 state、callback(fn.then)。
// 省略若干代码 export default function useAsyncFn<T extends FunctionReturningPromise>( fn: T, deps: DependencyList = [], initialState: StateFromFunctionReturningPromise<T> = { loading: false } ): AsyncFnReturn<T> { const lastCallId = useRef(0); const isMounted = useMountedState(); const [state, set] = useState<StateFromFunctionReturningPromise<T>>(initialState); const callback = useCallback((...args: Parameters<T>): ReturnType<T> => { const callId = ++lastCallId.current; if (!state.loading) { set((prevState) => ({ ...prevState, loading: true })); } return fn(...args).then( (value) => { isMounted() && callId === lastCallId.current && set({ value, loading: false }); return value; }, (error) => { isMounted() && callId === lastCallId.current && set({ error, loading: false }); return error; } ) as ReturnType<T>; }, deps); return [state, callback as unknown as T]; }React hook that resolves an async function or a function that returns a promise; 解析异步函数或返回
promise的函数的React钩子；
import { DependencyList, useEffect } from 'react'; import useAsyncFn from './useAsyncFn'; import { FunctionReturningPromise } from './misc/types'; export { AsyncState, AsyncFnReturn } from './useAsyncFn'; export default function useAsync<T extends FunctionReturningPromise>( fn: T, deps: DependencyList = [] ) { const [state, callback] = useAsyncFn(fn, deps, { loading: true, }); useEffect(() => { callback(); }, [callback]); return state; }useAsyncRetry docs | useAsyncRetry demo
Uses useAsync with an additional retry method to easily retry/refresh the async function; 重试
主要就是变更依赖，次数（attempt），变更时会执行 useAsync 的 fn 函数。
import { DependencyList, useCallback, useState } from 'react'; import useAsync, { AsyncState } from './useAsync'; export type AsyncStateRetry<T> = AsyncState<T> & { retry(): void; }; const useAsyncRetry = <T>(fn: () => Promise<T>, deps: DependencyList = []) => { const [attempt, setAttempt] = useState<number>(0); const state = useAsync(fn, [...deps, attempt]); const stateLoading = state.loading; const retry = useCallback(() => { // 省略开发环境警告提示 setAttempt((currentAttempt) => currentAttempt + 1); }, [...deps, stateLoading]); return { ...state, retry }; }; export default useAsyncRetry;useTimeoutFn 属于 Animations 模块，但这个 hook 在 useDebounce 中使用，所以放到这里讲述。
useTimeoutFn docs | useTimeoutFn demo
Calls given function after specified amount of milliseconds. 在指定的毫秒数后调用给定的函数。
主要是 useRef 和 setTimeout 结合实现的。
import { useCallback, useEffect, useRef } from 'react'; export type UseTimeoutFnReturn = [() => boolean | null, () => void, () => void]; export default function useTimeoutFn(fn: Function, ms: number = 0): UseTimeoutFnReturn { const ready = useRef<boolean | null>(false); const timeout = useRef<ReturnType<typeof setTimeout>>(); const callback = useRef(fn); const isReady = useCallback(() => ready.current, []); const set = useCallback(() => { ready.current = false; timeout.current && clearTimeout(timeout.current); timeout.current = setTimeout(() => { ready.current = true; callback.current(); }, ms); }, [ms]); const clear = useCallback(() => { ready.current = null; timeout.current && clearTimeout(timeout.current); }, []); // update ref when function changes useEffect(() => { callback.current = fn; }, [fn]); // set on mount, clear on unmount useEffect(() => { set(); return clear; }, [ms]); return [isReady, clear, set]; }useDebounce docs | useDebounce demo
React hook that delays invoking a function until after wait milliseconds have elapsed since the last time the debounced function was invoked. 防抖
import { DependencyList, useEffect } from 'react'; import useTimeoutFn from './useTimeoutFn'; export type UseDebounceReturn = [() => boolean | null, () => void]; export default function useDebounce( fn: Function, ms: number = 0, deps: DependencyList = [] ): UseDebounceReturn { const [isReady, cancel, reset] = useTimeoutFn(fn, ms); useEffect(reset, deps); return [isReady, cancel]; }useThrottle docs | useThrottle demo
React hooks that throttle.
节流
import { useEffect, useRef, useState } from 'react'; import useUnmount from './useUnmount'; const useThrottle = <T>(value: T, ms: number = 200) => { const [state, setState] = useState<T>(value); const timeout = useRef<ReturnType<typeof setTimeout>>(); const nextValue = useRef(null) as any; const hasNextValue = useRef(0) as any; useEffect(() => { if (!timeout.current) { setState(value); const timeoutCallback = () => { if (hasNextValue.current) { hasNextValue.current = false; setState(nextValue.current); timeout.current = setTimeout(timeoutCallback, ms); } else { timeout.current = undefined; } }; timeout.current = setTimeout(timeoutCallback, ms); } else { nextValue.current = value; hasNextValue.current = true; } }, [value]); useUnmount(() => { timeout.current && clearTimeout(timeout.current); }); return state; }; export default useThrottle;我们继续来看 UI 用户界面部分。
useFullscreen docs | useFullscreen demo
Display an element full-screen, optional fallback for fullscreen video on iOS. 实现全屏
主要使用 screenfull npm 包实现。
import { RefObject, useState } from 'react'; import screenfull from 'screenfull'; import useIsomorphicLayoutEffect from './useIsomorphicLayoutEffect'; import { noop, off, on } from './misc/util'; export interface FullScreenOptions { video?: RefObject< HTMLVideoElement & { webkitEnterFullscreen?: () => void; webkitExitFullscreen?: () => void } >; onClose?: (error?: Error) => void; } const useFullscreen = ( ref: RefObject<Element>, enabled: boolean, options: FullScreenOptions = {} ): boolean => { const { video, onClose = noop } = options; const [isFullscreen, setIsFullscreen] = useState(enabled); useIsomorphicLayoutEffect(() => { if (!enabled) { return; } if (!ref.current) { return; } const onWebkitEndFullscreen = () => { if (video?.current) { off(video.current, 'webkitendfullscreen', onWebkitEndFullscreen); } onClose(); }; const onChange = () => { if (screenfull.isEnabled) { const isScreenfullFullscreen = screenfull.isFullscreen; setIsFullscreen(isScreenfullFullscreen); if (!isScreenfullFullscreen) { onClose(); } } }; if (screenfull.isEnabled) { try { screenfull.request(ref.current); setIsFullscreen(true); } catch (error) { onClose(error); setIsFullscreen(false); } screenfull.on('change', onChange); } else if (video && video.current && video.current.webkitEnterFullscreen) { video.current.webkitEnterFullscreen(); on(video.current, 'webkitendfullscreen', onWebkitEndFullscreen); setIsFullscreen(true); } else { onClose(); setIsFullscreen(false); } return () => { setIsFullscreen(false); if (screenfull.isEnabled) { try { screenfull.off('change', onChange); screenfull.exit(); } catch {} } else if (video && video.current && video.current.webkitExitFullscreen) { off(video.current, 'webkitendfullscreen', onWebkitEndFullscreen); video.current.webkitExitFullscreen(); } }; }, [enabled, video, ref]); return isFullscreen; }; export default useFullscreen;我们继续来看 Lifecycles 生命周期部分。
useLifecycles docs | useLifecycles demo
React lifecycle hook that call mount and unmount callbacks, when component is mounted and un-mounted, respectively. React 生命周期挂钩，分别在组件安装和卸载时调用。
import { useEffect } from 'react'; const useLifecycles = (mount, unmount?) => { useEffect(() => { if (mount) { mount(); } return () => { if (unmount) { unmount(); } }; }, []); }; export default useLifecycles;useCustomCompareEffect docs | useCustomCompareEffect demo
A modified useEffect hook that accepts a comparator which is used for comparison on dependencies instead of reference equality. 一个经过修改的useEffect钩子，它接受一个比较器，该比较器用于对依赖项进行比较，而不是对引用相等进行比较。
import { DependencyList, EffectCallback, useEffect, useRef } from 'react'; const isPrimitive = (val: any) => val !== Object(val); type DepsEqualFnType<TDeps extends DependencyList> = (prevDeps: TDeps, nextDeps: TDeps) => boolean; const useCustomCompareEffect = <TDeps extends DependencyList>( effect: EffectCallback, deps: TDeps, depsEqual: DepsEqualFnType<TDeps> ) => { // 省略一些开发环境的警告提示 const ref = useRef<TDeps | undefined>(undefined); if (!ref.current || !depsEqual(deps, ref.current)) { ref.current = deps; } useEffect(effect, ref.current); }; export default useCustomCompareEffect;useDeepCompareEffect docs | useDeepCompareEffect demo
A modified useEffect hook that is using deep comparison on its dependencies instead of reference equality. 一个修改后的
useEffect钩子，它对其依赖项使用深度比较，而不是引用相等。
import { DependencyList, EffectCallback } from 'react'; import useCustomCompareEffect from './useCustomCompareEffect'; import isDeepEqual from './misc/isDeepEqual'; const isPrimitive = (val: any) => val !== Object(val); const useDeepCompareEffect = (effect: EffectCallback, deps: DependencyList) => { // 省略若干开发环境的警告提示 useCustomCompareEffect(effect, deps, isDeepEqual); }; export default useDeepCompareEffect;最后，我们来看 Animations 生命周期部分。
useUpdate docs | useUpdate demo
React utility hook that returns a function that forces component to re-render when called. React 实用程序钩子返回一个函数，该函数在调用时强制组件重新渲染。
主要用了 useReducer 每次调用 updateReducer 方法，来达到强制组件重新渲染的目的。
import { useReducer } from 'react'; const updateReducer = (num: number): number => (num + 1) % 1_000_000; export default function useUpdate(): () => void { const [, update] = useReducer(updateReducer, 0); return update; }行文至此，我们简单分析了若干 react-use 的自定义 React Hooks。想进一步学习的小伙伴，可以继续学完剩余的 hooks。还可以学习 ahooks、别人写的 ahooks 源码分析、 beautiful-react-hooks、mantine-hooks等。
学习过程中带着问题多查阅 React 新文档 react.dev，新中文文档 zh-hans.react.dev，相信收获更大。
如果技术栈是 Vue，感兴趣的小伙伴可以学习 VueUse。
如果能看完一些 React Hooks 工具集合库的源码。相信一定能对 React Hooks 有更深的理解，自己写自定义 React Hooks 时也会更加顺利、快速。
如果看完有收获，欢迎点赞、评论、分享支持。你的支持和肯定，是我写作的动力。
最后可以持续关注我@若川。另外，想学源码，极力推荐关注我写的专栏《学习源码整体架构系列》，目前是掘金关注人数（4.7k+人）第一的专栏，写有20余篇源码文章。
我倾力持续组织了一年多每周大家一起学习200行左右的源码共读活动，感兴趣的可以点此扫码加我微信 ruochuan02 参与。