react-use hooks源码学习前言在react开发中离不开各种hooks.熟悉常见的hooks工具库有助于提升

前言

在react开发中离不开各种hooks.熟悉常见的hooks工具库有助于提升开发效率，在应对一些需求也能封装一些可用的hooks，这次我们来学习下react-use这个库。

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。

步骤：

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。

Sensors行为：

useIdle

useIdle docs | useIdle demo

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';
// 节流
import { throttle } from 'throttle-debounce';
// 事件解绑和监听函数
import { off, on } from './misc/util';
// 监听的函数
const defaultEvents = ['mousemove', 'mousedown', 'resize', 'keydown', 'touchstart', 'wheel'];
// 闲置的时间
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;
    // 这里为什么需要localState？？？
    let localState: boolean = state;
    const set = (newState: boolean) => {
      if (mounted) {
        localState = newState;
        setState(newState);
      }
    };
    // 每次事件触发onEvent则会重新计时
    const onEvent = throttle(50, () => {
      if (localState) {
        set(false);
      }

      clearTimeout(timeout);
      timeout = setTimeout(() => set(true), ms);
    });
    const onVisibility = () => {
      // 只有在标签页展示时才会计时间
      if (!document.hidden) {
        onEvent();
      }
    };

    for (let i = 0; i < events.length; i++) {
      // 遍历事件，查看事件是否有被触发
      on(window, events[i], onEvent);
    }
    // 监听页面是否被隐藏
    on(document, 'visibilitychange', onVisibility);
    // 开始计时
    timeout = setTimeout(() => set(true), ms);

    return () => {
      // 将状态设置为unmounted
      mounted = false;
      // 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;

useLocation:

useLocation docs | useLocation demo

React sensor hook that tracks brower's location.主要获取 window.location 等对象信息。

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;

State状态

useFirstMountState

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 {
  // useRef在重新渲染值不会更改
  const isFirst = useRef(true);

  if (isFirst.current) {
    isFirst.current = false;

    return true;
  }

  return isFirst.current;
}

usePrevious

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改变并不会触发页面render，即函数不会重新运行，此时虽然值更新了，但是返回的值还是先前的值
    ref.current = state;
  });

  return ref.current;
}

useSet

useSet docs | useSet demo

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; // 添加
  remove: (key: K) => void; // 移除
  toggle: (key: K) => void; // 切换
  reset: () => void; // 重置
}

export interface Actions<K> extends StableActions<K> {
  has: (key: K) => boolean; // 判断是否存在某元素
}
// 接收Set，返回set集合和操作方法
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

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;

Side-effect

useAsyncFn

useAsyncFn docs | useAsyncFn demo

React hook that returns state and a callback for an async function or a function that returns a promise. The state is of the same shape as useAsync.

为异步函数或返回promise的函数返回状态和回调的React钩子。状态与useAsync的形状相同。

主要函数传入 Promise 函数 fn，然后执行函数 fn.then()。返回 state、callback(fn.then)。

/**
 * 
 * @param fn 接收的函数或者异步函数
 * @param deps 返回函数的依赖，依赖改变，返回函数会重新生成
 * @param initialState 初始state
 * @returns [state, callback as unknown as T]
 */
export default function useAsyncFn<T extends FunctionReturningPromise>(
  fn: T,
  deps: DependencyList = [],
  initialState: StateFromFunctionReturningPromise<T> = { loading: false }
): AsyncFnReturn<T> {
  const lastCallId = useRef(0);
  // useMountedState: 判断组件是否加载
  const isMounted = useMountedState();
  const [state, set] = useState<StateFromFunctionReturningPromise<T>>(initialState);

  const callback = useCallback((...args: Parameters<T>): ReturnType<T> => {
    // 保证最后一次回调的结果能匹配上最后的回调，竞态问题
    const callId = ++lastCallId.current;

    if (!state.loading) {
      set((prevState) => ({ ...prevState, loading: true }));
    }

    return fn(...args).then(
      (value) => {
        // 保证最后一次回调的结果能匹配上最后的回调，竞态问题
        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];
}

useAsync

useAsync docs | useAsync demo

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

useAsyncRetry docs | useAsyncRetry demo

Uses useAsync with an additional retry method to easily retry/refresh the async function; 使用useAsync额外·1返回支持重试/刷新的函数

主要就是变更依赖，次数（attempt），变更时会执行 useAsync 的 fn 函数。

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(() => {
    if (stateLoading) {
      if (process.env.NODE_ENV === 'development') {
        console.log(
          'You are calling useAsyncRetry hook retry() method while loading in progress, this is a no-op.'
        );
      }

      return;
    }

    setAttempt((currentAttempt) => currentAttempt + 1);
  }, [...deps, stateLoading]);

  return { ...state, retry };
};

useDebounce

防抖：就是指触发事件后 n 秒后才执行函数，如果在 n 秒内又触发了事件，则会重新计算函数执行时间。

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';
// 在指定的毫秒数后调用给定的函数。
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);
  // 取消上一次执行的函数
  useEffect(reset, deps);

  return [isReady, cancel];
}

useThrottle

节流：连续触发事件但是在 n 秒中只执行一次函数。节流会稀释函数的执行频率

useThrottle docs | useThrottle demo

React hooks that throttle. 节流

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 = () => {
        // 是否存在新的值， 存在则更新，不存在则清除定时器，让下一次值走更新
        if (hasNextValue.current) {
          hasNextValue.current = false;
          // 更新值
          setState(nextValue.current);
          timeout.current = setTimeout(timeoutCallback, ms);
        } else {
          timeout.current = undefined;
        }
      };
      timeout.current = setTimeout(timeoutCallback, ms);
    } else {
      // 如果当前还在运行定时器，则记录新的value，写一次赋值给state
      nextValue.current = value;
      // 存在新值
      hasNextValue.current = true;
    }
  }, [value]);

  useUnmount(() => {
    // 清除定时器
    timeout.current && clearTimeout(timeout.current);
  });

  return state;
};

UI 用户界面

useFullscreen

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.

const useFullscreen = (
  ref: RefObject<Element>,
  enabled: boolean,
  options: FullScreenOptions = {}
): boolean => {
  const { video, onClose = noop } = options;
  const [isFullscreen, setIsFullscreen] = useState(enabled);
  // const useIsomorphicLayoutEffect = isBrowser ? useLayoutEffect : useEffect;
  useIsomorphicLayoutEffect(() => {
    if (!enabled) {
      return;
    }
    if (!ref.current) {
      return;
    }

    const onWebkitEndFullscreen = () => {
      if (video?.current) {
        // 关闭事件监听
        off(video.current, 'webkitendfullscreen', onWebkitEndFullscreen);
      }
      onClose();
    };

    const onChange = () => {
      if (screenfull.isEnabled) {
        const isScreenfullFullscreen = screenfull.isFullscreen;
        setIsFullscreen(isScreenfullFullscreen);
        if (!isScreenfullFullscreen) {
          onClose();
        }
      }
    };
    // 是否支持全屏
    if (screenfull.isEnabled) {
      try {
        // .request(element, options?) Make an element fullscreen. Accepts a DOM element and FullscreenOptions.The default element is <html>. 
        // If called with another element than the currently active, it will switch to that if it's a descendant.
        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;
};

LiCycles生命周期

useLifecycles

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

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

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;

Animations动画

useUpdate

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;
}

总结

虽然没有全部hooks看完，但是通过分析若干react-use的自定义React hooks，也是有了很大的收获。

react-use hooks源码学习

前言

目录：

步骤：