React自定義hook的方法

import { useEffect, useState } from "react";

//定義size物件
interface WindowSize {
    width: number,
    height: number
}
const useWindowSize = () => {
    const [size, setSize] = useState<WindowSize>({
        width: document.documentElement.clientWidth,
        height: document.documentElement.clientHeight
    })

    useEffect(() => {
        //監聽size變化
        window.addEventListener('resize', () => {
            setSize({
                width: document.documentElement.clientWidth,
                height: document.documentElement.clientHeight
            })
        })
        return () => {
            //元件銷燬時移除監聽
            window.removeEventListener('resize', () => {
                setSize({
                    width: document.documentElement.clientWidth,
                    height: document.documentElement.clientHeight
                })
            })
        }
    },[])
    return size
}
export default useWindowSize

import useWindowSize from './hooks/useWindowSize';
function App() {
  const size = useWindowSize()
  return (
    <div>
      <div>頁面寬度：{size.width}</div>
      <div>頁面高度：{size.height}</div>
    </div>
  )
}
export default App

import { useEffect, useState } from "react"

//定義偏移量物件
interface ScrollOffset {
    x: number,
    y: number
}

const useWindowScroll = () => {
    const [off, setOff] = useState<ScrollOffset>({
        x: window.scrollX, 
        y: window.scrollY
    })
    useEffect(() => {
        //監聽
        window.addEventListener('scroll', () => {
            setOff({
                x: window.scrollX,
                y: window.scrollY
            })
        })
        return () => {
            //移除監聽
            window.removeEventListener('scroll', () => {
                setOff({
                    x: window.scrollX,
                    y: window.scrollY
                })
            })
        }
    })
    return off
}
export default useWindowScroll

import useWindowScroll from './hooks/useWindowScroll';
function App() {
  const offSet = useWindowScroll()

  return (
    <div style={{height: '10000px', width: '10000px'}}>
      <div>捲動y：{offSet.y}</div>
      <div>捲動x：{offSet.x}</div>
    </div>
  )
}

export default App

import { useEffect, useState } from "react"

const useLocalStorage = (key: string, defaultValue: string) : ([string, React.Dispatch<React.SetStateAction<string>>]) => {
    const [value, setValue] = useState(defaultValue)
    useEffect(() => {
        window.localStorage.setItem(key, value)
    },[key, value])
    return [value, setValue]
}

export default useLocalStorage

import useLocalStorage from './hooks/useLocalStorage';

function App() {

  const [value, setValue] = useLocalStorage('key', 'react')

  return (
    <div>

    <button onClick={() => {
        //點選修改value，會自動同步至本地
        setValue('vue')
      }}>點選</button>
      <div>{ value }</div>
    </div>
  )
}
export default App