Gatsby -未定义IntersectionObserver

Question

我正在尝试构建我的gatsby项目，但由于IntersectionObserver不被识别，我无法构建。我在InView组件中使用intersectionObserver：

import React, { useRef, useState, useEffect } from 'react'


const InView = ({ children }) => {
    const [boundingClientY, setBoundingClientY] = useState(null)
    const [direction, setDirection] = useState(null)
    const [element, setElement] = useState(null)
    const [inView, setInView] = useState(false)



    const observer = useRef(new IntersectionObserver((entries) => {
        const first = entries[0]
        const { boundingClientRect } = first
        first.isIntersecting && setInView(true)
        !first.isIntersecting && setInView(false)
        boundingClientRect.y > boundingClientY && setDirection('down')
        boundingClientRect.y < boundingClientY && setDirection('up')
        boundingClientY && setBoundingClientY(first.boundingClientRect.y)

    }))


    useEffect(() => {
        const currentElement = element
        const currentObserver = observer.current
        currentElement && currentObserver.observe(currentElement)
        // console.log(currentObserver)
        return () => {
            currentElement && currentObserver.unobserve(currentElement)
        };
    }, [element])

    const styles = {
        opacity: inView ? 1 : 0,
        transform: `
            translateY(${!inView ?
                direction === 'up' ? '-20px' : '20px'
                : 0})
            rotateY(${!inView ? '35deg' : 0})
            scale(${inView ? 1 : 0.9})
            `,
        transition: 'all 0.4s ease-out 0.2s'
    }

    return (
        <div ref={setElement} style={styles}>

            {children}

        </div>
    )
}

export default InView

我有一个用于根元素的包装器来启用全局状态，并尝试在gatsby-browser.js中导入polyfill：

import React from 'react'
import GlobalContextProvider from './src/components/context/globalContextProvider'

export const wrapRootElement = ({ element }) => {
    return (
        <GlobalContextProvider>
            {element}
        </GlobalContextProvider>
    )
}

export const onClientEntry = async () => {
    if (typeof IntersectionObserver === `undefined`) {
        await import(`intersection-observer`);
    }
}

Answer 1

这是构建时的错误，对吗($ gatsby构建)？如果是这样的话，这与浏览器支持无关。

事实是，IntersectionObserver是一个浏览器API，您不应该在服务器端呈现期间使用浏览器API。取而代之的是，您尝试在组件挂载之后使用它们。为了解决这个问题，在useEffect()中初始化你的观察者，而不是像你现在做的那样使用useRef()。

...
const observer = useRef();

useEffect(() => {
  observer.current = new IntersectionObserver({ ... });
}, []); // do this only once, on mount
...

Answer 2

声明一个let变量= null。这也适用于NextJS

...
let observer = null

useEffect(()=> {
observer = new IntersectionObserver(callback,optional);
},[])