Change 'currentBoard' for whatever board you want to parse, you can run this script concurrently in other child processes, just make sure the intervals don't line up exactly and that you are not making more than 1 request a second.

4chanActivityTracker.js

const https = require('https'),
    colors = require('colors'),
    moment = require('moment')

const catalogPromise = (board) => {
    return new Promise((resolve, reject) => {
        let path = `/${board}/catalog.json`
        let url = `https://a.4cdn.org${path}`
        let req = https.request({
            host: 'a.4cdn.org',
            path: path,
            port: 443,
            method: 'GET',
        }, (res) => {
            let data = ''
            res.on('data', (chunk) => {
                data = data.concat(chunk)
            })
            res.on('end', () => {
                try {
                    let jsonRes = JSON.parse(data)
                    resolve(jsonRes)
                } catch (err) {
                    reject(`failed to parse data:\n${util.inspect(data)}\n`)
                }
            })
        })
        req.on('error', (err) => {
            reject(err)
        })
        req.end()
    })
}

let currentBoard = 'pol'

let lastThreads = []
let currentThreads = undefined

setInterval(() => {
    console.log('\n\n\n')
    catalogPromise(currentBoard).then(pages => {
        if (currentThreads !== undefined) {
            lastThreads = currentThreads
        }
        currentThreads = []
        pages.forEach((page, pageIndex) => {
            page.threads.forEach((thread, threadIndex) => {
                currentThreads.push([`https://boards.4chan.org/${currentBoard}/thread/${thread.no}`, (thread.replies / (((new Date().getTime() - thread.tim) / 1000) / 60)).toFixed(2)])
            })
        })
        currentThreads.sort((a, b) => {
            return a[1] - b[1]
        })
        currentThreads.forEach((thread, threadIndex) => {
            lastThreads.forEach((lastThread, lastThreadIndex) => {
                if(thread[0] === lastThread[0]){
                    if((threadIndex - lastThreadIndex) > 0){
                        console.log(`${thread[0]} ${thread[1]} ${threadIndex - lastThreadIndex}`.green)
                    }else if((threadIndex - lastThreadIndex) === 0){
                        console.log(`${thread[0]} ${thread[1]}`)
                    }else{
                        console.log(`${thread[0]} ${thread[1]} ${threadIndex - lastThreadIndex}`.red)
                    }
                }
            })
        })
    }).catch(err => {
        console.log(err)
    })
}, 10000)