fetch_instagram_followers_info.js

/**
 *
 * @param pageName - Page name you want to check
 * @returns Object { followers, followings, accountsNotFollowBack }
 */
async function getListOfPeopleWhoNotFollow(pageName) {
    let username = pageName; // your page name, mine is oisee_gallery
    try {
        console.log("Fetching data....");
        let res = await fetch(`https://www.instagram.com/${username}/?__a=1`)

        res = await res.json()
        let userId = res.graphql.user.id

        console.log("Getting followers");
        let after = null,
            has_next = true
        while (has_next) {
            await fetch(`https://www.instagram.com/graphql/query/?query_hash=c76146de99bb02f6415203be841dd25a&variables=` + encodeURIComponent(JSON.stringify({
                id: userId,
                include_reel: true,
                fetch_mutual: true,
                first: 50,
                after: after
            }))).then(res => res.json()).then(res => {
                has_next = res.data.user.edge_followed_by.page_info.has_next_page
                after = res.data.user.edge_followed_by.page_info.end_cursor
                followers = followers.concat(res.data.user.edge_followed_by.edges.map(({
                    node
                }) => {
                    return node.username
                }))
            })
        }

        console.log("Getting followings");
        has_next = true
        after = null
        while (has_next) {
            await fetch(`https://www.instagram.com/graphql/query/?query_hash=d04b0a864b4b54837c0d870b0e77e076&variables=` + encodeURIComponent(JSON.stringify({
                id: userId,
                include_reel: true,
                fetch_mutual: true,
                first: 50,
                after: after
            }))).then(res => res.json()).then(res => {
                has_next = res.data.user.edge_follow.page_info.has_next_page
                after = res.data.user.edge_follow.page_info.end_cursor
                followings = followings.concat(res.data.user.edge_follow.edges.map(({
                    node
                }) => {
                    return node.username
                }))
            })
        }
        console.log("Gettings accounts that do not follow back...");
        accountsNotFollowBack = followings.filter(fname => !followers.includes(fname));
        console.log('accounts that don\'t follow back: ', accountsNotFollowBack);
        return {
            followers,
            followings,
            accountsNotFollowBack
        };
    } catch (err) {
        console.log('Invalid username')
    }
}


async function StartProcess() {

    try {
        console.log("Starting the process");
        // select following button to open the dialog
        var xpath = "//div[text()=' following']";
        var matchingElement = document.evaluate(xpath, document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue;
        matchingElement.click();
        await new Promise(r => setTimeout(r, 2000));

        let followingList = await getFollowings();
        let unfollowersLeft = accountsNotFollowBack.map(x => x.trim());

        while (unfollowersLeft.length > 0) {
            const currUserToUnfollow = unfollowersLeft[0];
            console.log("Currently trying to unfollow: ", currUserToUnfollow);
            if (followingList[currUserToUnfollow]) {
                followingList[currUserToUnfollow].click();
                await new Promise(r => setTimeout(r, 1500));
                const unfollowConfirmBtn = document.querySelector('.aOOlW.-Cab_');
                // sleep for some time
                await new Promise(r => setTimeout(r, 1500));
                unfollowConfirmBtn.click();
                const unfollowedUser = unfollowersLeft.shift();
                console.log("Unfollowed :", unfollowedUser);
                await new Promise(r => setTimeout(r, 2000));
            } else {
                await ScrollDown();
                followingList = await getFollowings();
            }
            console.log("People remaining: ", unfollowersLeft.length);
        }
    } catch (err) {
        console.log("Error while unfollowing: ", err);
    }
}

async function getFollowings() {
    try {
        const followingListItems = document.querySelector('div[aria-label="Following"]').childNodes[0].childNodes[0].childNodes[2].childNodes[0].childNodes[0].childNodes;
        let followingsDict = {};
        for (let li of followingListItems) {
            const innerButtonElem = li.childNodes[0].childNodes[1].childNodes[0];

            let username = '';
            try {
                userName = li.childNodes[0].childNodes[1].childNodes[0].childNodes[0].childNodes[0].childNodes[0].childNodes[0].innerText;
            } catch {
                userName = li.childNodes[0].childNodes[0].childNodes[1].childNodes[0].childNodes[0].childNodes[0].childNodes[0].innerText;
            }
            username = username.trim();
            followingsDict[userName] = innerButtonElem;
        }
        return followingsDict;
    } catch (err) {
        console.error("Error occurred while getting new elements from dialog list. Err: ", err);
    }
}


async function ScrollDown() {
    try {
        console.log("Finding more accounts to unfollow...");
        await new Promise(r => setTimeout(r, 2500));
        const scroll_stuff = document.querySelector('div[aria-label="Following"]').childNodes[0].childNodes[0].childNodes[2];
        scroll_stuff.scrollTop = scroll_stuff.scrollHeight;

    } catch (err) {
        console.error("Error occurred while ScrollDown() Errr: ", err);
    }
}

// Bismillah
const { followers, followings, accountsNotFollowBack } = await getListOfPeopleWhoNotFollow('oisee_gallery');
await StartProcess();

Getting error:
Uncaught TypeError: Cannot destructure property 'followers' of '(intermediate value)' as it is undefined.
at :143:9