react版模拟亚马逊人机交互菜单的实现

const [active, setActive] = useState(null) // 选中的菜单
  const [showSub, setShowSub] = useState(false) // 是否显示子菜单
  let timeout = useRef(null) //  设置延迟定时器，防止鼠标移到tab内容经过菜单时的切换
  let mouseLocs = useRef([]) // 记录鼠标移动时的坐标数组
  let firstSlope = useRef(null) // 菜单栏的固定点1， 根据菜单栏和内容的位置而改变
  let secondSlope = useRef(null) // 菜单栏的固定点2， 根据菜单栏和内容的位置而改变
  const refNavigation = useRef(null)
  const refNav = useRef(null)
  const refSubnav = useRef(null)


  
  function proPosInTriangle(p1, p2, p3, m) {
    // 结束时鼠标坐标位置
    let x = m.x,
      y = m.y,
      // 开始鼠标坐标位置
      x1 = p1.x,
      y1 = p1.y,
      // 菜单栏包裹层右上角坐标
      x2 = p2.x,
      y2 = p2.y,
      // 右下角坐标
      x3 = p3.x,
      y3 = p3.y,
      // (y2 - y1) / (x2 - x1)为两坐标连成直线的斜率
      // 因为直线的公式为y=kx+b;当斜率相同时，只要比较
      // b1和b2的差值就可以知道该点是在
      // (x1,y1),(x2,y2)的直线的哪个方向
      // 当r1大于0，说明该点在直线右侧，其它以此类推
      r1 = y - y1 - ((y2 - y1) / (x2 - x1)) * (x - x1),
      r2 = y - y2 - ((y3 - y2) / (x3 - x2)) * (x - x2),
      r3 = y - y3 - ((y1 - y3) / (x1 - x3)) * (x - x3),
      compare

    compare = r1 * r2 * r3 < 0 && r1 > 0
    // 返回是否在三角形内的结果
    return compare
  }

  
  function LocFromdoc(element) {
    const { x, y, width, height } = element.getBoundingClientRect()
    return {
      x: x,
      y: y,
      width,
      height,
    }
  }
  
  function getInfo(element) {
    const location = LocFromdoc(element)
    return {
      top: location.y,
      topAndHeight: location.y + element.offsetHeight, // offsetHeight 元素的像素高度, 高度包含该元素的垂直内边距和边框，且是一个整数
      left: location.x,
      leftAndWidth: location.x + element.offsetWidth,
    }
  }
  
  function ensureTriangleDots() {
    // 获取菜单栏的位置
    const info = getInfo(refNav.current)
    const x1 = info.leftAndWidth
    const y1 = info.top
    const x2 = x1
    const y2 = info.topAndHeight

    firstSlope.current = {
      x: x1,
      y: y1,
    }
    secondSlope.current = {
      x: x2,
      y: y2,
    }
  }

  const onMouseOver = useCallback(
    obj => {
      let diff
      try {
        // 是否在指定三角形内
        diff = proPosInTriangle(
          mouseLocs.current[0],
          firstSlope.current,
          secondSlope.current,
          mouseLocs.current[2]
        )
      } catch (ex) {}
      // 是就启动延迟显示，
      // 否则不延迟
      if (diff) {
        timeout.current = setTimeout(() => {
          setActive(obj.key)
          setShowSub(true)
        }, 300)
      } else {
        setActive(obj.key)
        setShowSub(true)
      }
    },
    [mouseLocs, timeout]
  )

  const onMouseEnter = () => {
    // 计算位置
    if (refNav.current) {
      ensureTriangleDots()
    }
    setShowSub(true)
  }

  // 移出菜单所在区域
  const onMouseLeave = () => {
    if (refSubnav.current) {
      setActive(null)
      setShowSub(false)
    }
  }

  // 记录鼠标在菜单栏中移动的最后三个坐标位置
  const onMousemove = event => {
    mouseLocs.current.push({
      x: event.pageX,
      y: event.pageY,
    })
    if (mouseLocs.current.length > 3) {
      // 移除超过三项的数据
      mouseLocs.current.shift()
    }
  }
  // 鼠标移出的时候，清除延时器
  const onMouseout = () => {
    if (timeout.current) {
      clearTimeout(timeout.current)
    }
  }