React 常见 hooks 的实现

usePrevious

记录之前的值。

import { useEffect, useRef } from "react"
function usePrevious<T>(value: T) {
  const ref = useRef<T>()
  useEffect(() => {
    ref.current = value
  }, [value])
  return ref.current
}

useOnClickOutside

点击元素外，隐藏元素。

type PossibleEvent = {
  [Type in HandledEventsType]: HTMLElementEventMap[Type]
}[HandledEventsType]
type Handler = (event: PossibleEvent) => void
function useOnClickOutside(
    ref: React.RefObject<HTMLElement>,
  handler: Handler) {
  useEffect(
    () => {
      const listener = (event) => {
        if (!ref.current || ref.current.contains(event.target)) {
          return
        }
        handler(event)
      }
      document.addEventListener("mousedown", listener)
      document.addEventListener("touchstart", listener)
      return () => {
        document.removeEventListener("mousedown", listener)
        document.removeEventListener("touchstart", listener)
      };
    },
    [ref, handler]
  )
}

完善版: use-onclickoutside。

useWindowSize

import { useState, useEffect } from "react"
interface Size {
  width: number | undefined;
  height: number | undefined;
}
function useWindowSize(): Size {
  // Initialize state with undefined width/height so server and client renders match
  // Learn more here: https://joshwcomeau.com/react/the-perils-of-rehydration/
  const [windowSize, setWindowSize] = useState<Size>({
    width: undefined,
    height: undefined,
  })
  useEffect(() => {
    function handleResize() {
      setWindowSize({
        width: window.innerWidth,
        height: window.innerHeight,
      })
    }
    window.addEventListener("resize", handleResize);
    handleResize()
    return () => window.removeEventListener("resize", handleResize)
  }, [])
  return windowSize;
}