I want to use Utterances for my blog. It should only load when someone scrolled to the bottom of the post so I use react-intersection-observer for that. I have made the following hook.

useUtterances.ts

import React from 'react'
import { useTheme } from 'next-themes'

import { siteMetadata } from '@/_data/index'

export const useUtterances = (commentNodeId: string) => {
    const config = siteMetadata.comment.utterancesConfig
    // username/repo format
    const REPO_NAME = config.repo as string

    const { theme, resolvedTheme } = useTheme()
    const utterancesTheme =
        theme === 'light' || resolvedTheme === 'light' ? config.theme : config.darkTheme

    React.useEffect(() => {
        const scriptParentNode = document.getElementById(commentNodeId)
        if (!scriptParentNode) return

        // docs - https://utteranc.es/
        const script = document.createElement('script')
        script.src = 'https://utteranc.es/client.js'
        script.async = true
        script.setAttribute('repo', REPO_NAME)
        script.setAttribute('issue-term', 'pathname')
        script.setAttribute('label', 'comment :speech_balloon:')
        script.setAttribute('theme', utterancesTheme)
        script.setAttribute('crossorigin', 'anonymous')

        scriptParentNode.appendChild(script)

        return () => {
            // cleanup - remove the older script with previous theme
            scriptParentNode.removeChild(scriptParentNode.firstChild as Node)
        }
    }, [REPO_NAME, commentNodeId, utterancesTheme])
}

Utterances.tsx

import React from 'react'
import { useInView } from 'react-intersection-observer'

import { useUtterances } from '@/hooks/useUtterances'

export const Utterances = () => {
    const COMMENTS_NODE_ID = 'comments'
    const { ref, inView } = useInView({ threshold: 0, triggerOnce: true })

    useUtterances(inView ? COMMENTS_NODE_ID : '')

    return (
        <div ref={ref} className="min-h-[400px]">
            {inView ? <div id={COMMENTS_NODE_ID} /> : null}
        </div>
    )
}

I use next-themes to toggle DarkMode. I also send a request to utterances iframe so it doesn't load script twice but it still loads it twice by unmounting & mounting the component.

DarkMode.tsx

import React from 'react'
import { useTheme } from 'next-themes'
import { MoonIcon, SunIcon } from '@heroicons/react/solid'

import { useHasMounted } from '@/hooks/index'
import { siteMetadata } from '@/_data/index'

export const DarkMode = () => {
    const { resolvedTheme, setTheme } = useTheme()
    const hasMounted = useHasMounted()

    const label = resolvedTheme === 'dark' ? 'Activate light mode' : 'Activate dark mode'

    if (!hasMounted) return null

    const toggleTheme = () => {
        const newTheme = resolvedTheme === 'light' ? 'dark' : 'light'
        setTheme(newTheme)

        // for utterances
        const frame = document.getElementsByClassName('utterances-frame')[0] as HTMLIFrameElement
        if (frame?.contentWindow) {
            const utterancesTheme =
                resolvedTheme === 'light'
                    ? siteMetadata.comment.utterancesConfig.darkTheme
                    : siteMetadata.comment.utterancesConfig.theme
            frame.contentWindow.postMessage({ type: 'set-theme', theme: utterancesTheme }, '*')
        }
    }

    return (
        <>
            <button
                className="focus:outline-none"
                type="button"
                title={label}
                aria-label={label}
                onClick={toggleTheme}
            >
                {resolvedTheme === 'light' ? (
                    <MoonIcon className="w-8 h-8" />
                ) : (
                    <SunIcon className="w-8 h-8" />
                )}
            </button>
        </>
    )
}

How do I make sure it only requests script once? It now calls it everytime I toggle. It mounts and unmounts the component as I see nothing for a while when the script is loading.

GitHub repo -> https://github.com/deadcoder0904/next-utterances-script-loads-twice/tree/master

Stackblitz demo -> https://stackblitz.com/edit/github-6frqvs?file=pages%2Findex.tsx

Open in New Window to see the Dark Mode as Stackblitz currently doesn't support Tailwind Dark Mode. Check the Network Tab to see it sends request everytime even though you can also see the Comments component mounting & unmounting.

How do I only load script once?