@haensl/react-hooks

Assorted React hooks.

Installation

Via `npm`

$ npm install -S @haensl/react-hooks

Via `yarn`

$ yarn add @haensl/react-hooks

Usage

Install @haensl/react-hooks
Use hooks in your components:

import { useDebounce } from '@haensl/react-hooks';

const DebouncedButton = () => {
  const handler = useDebounce(() => {
    console.log('click');
  }, 50);

  return (
    <button
      onClick={ handler }
    >click me</button>
  );
};

Available hooks

useAnimationFrame: animate a function.
useBoundingClientRect: keep track of a container's DOM rectangle.
useClassNames: compile CSS class names from state.
useDebounce: debounce a function.
useInterval: use an interval.
useIsMounted: keep track of whether or not a component is mounted.
useIsomorphicLayoutEffect: use this instead of useLayoutEffect if your app uses serverside rendering (SSR).
useIsScrolling: keep track of whether or not the user is scrolling.
useLang: use the browser's language setting.
useOnScroll: subscribe to scroll events.
usePrevious: keep track of a variable's previous value.
useTimeout: use a timeout.
useWindowScroll: keep track of the window's scroll position.
useWindowSize: keep track of the window's size.

`useAnimationFrame(fn)`

Uses requestAnimationFrame to animate a function fn. The callback is passed one single argument, the time delta in milliseconds that has passed between this and the last call. Please check the example below as well as the Codepen example.

Example

import React, { useState, useEffect } from 'react';
import { useAnimationFrame } from '@haensl/react-hooks';

const AnimatedTimer = () => {
  const [seconds, setSeconds] = useState(0);
  const [elapsed, setElapsed] = useState(0);

  useAnimationFrame((dt) => {
    setElapsed(elapsed + dt);
  });

  useEffect(() => {
    if (elapsed >= 1000) {
      setSeconds(seconds + 1);
      setElapsed(elapsed - 1000);
    }
  }, [elapsed]);

  return (
    <span>{ seconds }</span>
  );
};

→ Codepen example

`useBoundingClientRect(ref, [debounceMs = 25])`

Returns the DOM rectangle (initially null) as returned by getBoundingClientRect for the given container ref. Changes are debounced by 25 milliseconds by default. Customize the debounce interval via the optional debounceMs argument. Please check out the example below as well as the Codepen example.

Example

import React, { useRef } from 'react';
import { useBoundingClientRect } from '@haensl/react-hooks';

const RectTracker = () => {
  const ref = useRef();
  const containerRect = useBoundingClientRect(ref);

  if (!containerRect) {
    return (
      <div ref={ ref }>
        <span>no container rect</span>
      </div>
    );
  }

  return (
    <div ref={ ref }>
      <span>Container rect:</span>
      <span>Width: {containerRect.width}</span>
      <span>Height: {containerRect.height}</span>
    </div>
  );
};

→ Codepen example

`useClassNames(states, [separator = ' '])`

Compiles a states object into a CSS class name string. By default all keys in states are joined by a space (' ') but you can supply a custom separator to cater to the needs of your CSS module naming methodology of choice. Please check the examples below.

Example

import React, { useState } from 'react';
import { useClassNames } from '@haensl/react-hooks';

const MyComponent = () => {
  const [stateA, setStateA] = useState(false);
  const className = useClassNames({
    MyComponent: true, // always have MyComponent in class name
    MyComponent--stateA: stateA // add MyComponent--stateA when stateA is true
  });

  // className will be 'MyComponent' or 'MyComponent MyComponent--stateA'

  return (
    <div className={ className }>
      {
        // render content
      }
    </div>
  );
};

Example: custom separator

import React, { useState } from 'react';
import { useClassNames } from '@haensl/react-hooks';

const MyComponent = () => {
  const [stateA, setStateA] = useState(false);
  const className = useClassNames(
    {
      MyComponent: true, // always have MyComponent in class name
      stateA // add --stateA when stateA is true
    },
    '--'
  );

  // className will either be 'MyComponent' or 'MyComponent--stateA'

  return (
    <div className={ className }>
      {
        // render content
      }
    </div>
  );
};

`useDebounce(fn, debounceMs)`

Uses memoization to debounce fn by debounceMs milliseconds. Please check the example below as well as the Codepen example.

Example

import React from 'react';
import { useDebounce } from '@haensl/react-hooks';

const DebouncedButton = () => {
  const handler = useDebounce(() => {
    console.log('click');
  }, 50); // handler only fires when there were no calls for 50ms.

  return (
    <button
      onClick={ handler }
    >click me</button>
  );
};

→ Codepen example

`useInterval(fn, intervalMs)`

Calls a fn repeatedly every intervalMs milliseconds.

Example

import React, { useState, useCallback } from 'react';
import { useInterval } from '@haensl/react-hooks';

const MyAnimation = () => {
  const [frame, setFrame] = useState(0);

  // Update frame every 100 milliseconds
  useInterval(() => {
    setFrame((frame) => frame + 1);
  }, 100);

  return (
    <div>{ frame }</div>
  );
};

`useIsMounted()`

Returns a function to check whether or not the component invoking the hook is mounted.

Example

import React, { useEffect } from 'react';
import { useIsMounted } from '@haensl/react-hooks';
import api from 'somewhere';

const MyComponent = () => {
  const isMounted = useIsMounted();
  // load some data from the backend
  useEffect(() => {
    api.fetchData()
      .then((data) => {
        if (isMounted()) {
          // use data only if component is still mounted
        }
      });
  }, []);
}

`useIsomorphicLayoutEffect(fn, deps)`

This hooks resolves the common React warning when using useLayoutEffect in a serverside environment:

Warning: useLayoutEffect does nothing on the server, because its effect cannot be encoded into the server renderer’s output format. This will lead to a mismatch between the initial, non-hydrated UI and the intended UI. To avoid this, useLayoutEffect should only be used in components that render exclusively on the client. See https://fb.me/react-uselayouteffect-ssr for common fixes.

useIsomorphicLayoutEffect resolves to useLayoutEffect on the client and useEffect on the server. Use this hook instead of useLayoutEffect if your app uses serverside rendering (SSR).

Example

import React, { useRef } from 'react';
import { useIsomorphicLayoutEffect } from '@haensl/react-hooks';

const MyComponent = () => {
  const ref = useRef();

  // prevents serverside rendering warning
  useIsomorphicLayoutEffect(() => {
    if (ref.current) {
      // do stuff with ref
    }
  }, [ref]);

  return (
    <div ref={ ref }>
      // ...
    </div>
  )
}

`useIsScrolling([el = window, scrollEndMs = 100])`

Returns a boolean indicating whether or not the user is scrolling. You can subscribe to a specific element via the first argument, el (default: window). End of scrolling is determined by no incoming scroll events for scrollEndMs milliseconds (default: 100). Please check the example blow as well as the Codepen example

Example

import React from 'react';
import { useIsScrolling } from '@haensl/react-hooks';

const UserScrollTracker = () => {
  const isScrolling = useIsScrolling();

  return (
    <span>The user is currently { isScrolling ? '' : 'not' } scrolling</span>
  );
};

→ Codepen example

`useLang({ defaultLang = 'en' }) => string`

Returns the user's language setting from navigator.language. Use the defaultLang of the options parameter to set a default language. (default: 'en).

Example

import React from 'react';
import { useLang } from '@haensl/react-hooks';

const MyComponent = () => {
  const lang = useLang();

  return (
    <span>The user's preferred language is { lang }.</span>
  );
};

`useOnScroll(fn, [el = window])`

Subscribes to scroll events on the given element el (default: window). The callback function fn is passed the Event. Please check the example below as well as the Codepen example.

Example

import React, { useState } from 'react';
import { useOnScroll } from '@haensl/react-hooks';

const WindowScrollTracker = () => {
  const [windowScroll, setWindowScroll] = useState(0);

  useOnScroll(() => {
    setWindowScroll(window.scrollY);
  });

  return (
    <div className="WindowScrollTracker">
      <span>Window has scrolled down</span>
      <span>{ windowScroll }px</span>
    </div>
  );
};

→ Codepen example

`usePrevious(value)`

Keeps track of changes to a value, storing it's previous state.

Example

import { useEffect, useState } from 'react';
import { usePrevious, useWindowScroll } from '@haensl/react-hooks';

const ScrollDirectionTracker = () => {
  const scrollPosition = useWindowScroll();
  const previousScrollPosition = usePrevious(scrollPosition);
  const [scrollDirection, setScrollDirection] = useState('down');

  useEffect(() => {
    if (previousScrollPosition.y < scrollPosition.y) {
      setScrollDirection('down');
    } else if (previousScrollPosition.y > scrollPosition.y) {
      setScrollDirection('up');
    }
  }, [scrollPosition, previousScrollPosition]);

  return (
    <div className="ScrollDirectionTracker">
      <span>User is scrolling</span>
      <span>{ scrollDirection }px</span>
    </div>
  );
};

`useTimeout(fn, timeoutMs = 0)`

Calls fn once after intervalMs milliseconds.

Example

import React, { useState, useCallback } from 'react';
import { useClassNames, useTimeout } from '@haensl/react-hooks';

const MyComponent = () => {
  const [animate, setAnimate] = useState(false);

  // Start animation after 1s
  useTimeout(() => {
    setAnimate(true);
  }, 1000);

  const className = useClassNames({
    animate
  });

  return (
    <div
        className={ className }
    >
        // ...
    </div>
  );
};

`useWindowScroll([debounceMs = 25])`

Returns an object (null if there is no window) with properties x and y reflecting the the scroll position of the window or document. Scroll position updates are by default debounced by 25 milliseconds. This debounce interval can be customized via the optional debounceMs argument. Please check the example below as well as the Codepen example.

Example

import React, { useState } from 'react';
import { useWindowScroll } from '@haensl/react-hooks';

const windowScrollTracker = () => {
  const windowScroll = useWindowScroll();

  if (!windowScroll) {
    return (
      <div className="WindowScrollTracker">
        no scroll poistion
      </div>
    );
  }

  return (
    <div className="WindowScrollTracker">
      <span>Scroll x: {windowScroll.x}</span>
      <span>Scroll y: {windowScroll.y}</span>
    </div>
  );
};

→ Codepen example

`useWindowSize([debounceMs = 25])`

Returns an object (initially null) with properties width and height reflecting the innerWidth and innerHeight of the window object. Size updates are by default debounced by 25 milliseconds. This debounce interval can be customized via the optional debounceMs argument. Please check the example below as well as the Codepen example.

Example

import React, { useState } from 'react';
import { useWindowSize } from '@haensl/react-hooks';

const WindowSizeTracker = () => {
  const windowSize = useWindowSize();

  if (!windowSize) {
    return (
      <div className="WindowSizeTracker">
        <span>No window size</span>
      </div>
    );
  }

  return (
    <div className="WindowSizeTracker">
      <span>Window Size:</span>
      <span>width: { windowSize.width }px</span>
      <span>height: { windowSize.height }px</span>
    </div>
  );
};