Tampermonkey script for filtering slack messages by user

slack_filter.user.js

// ==UserScript==
// @name         Slack filter messages by UID
// @namespace    Slack
// @version      0.1
// @description  removes messages from unwanted people in slack channels and threads, or replaces them with kittens
// @author       Octaharon <Alexander Uskov>
// @include      https://app.slack.com/client/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    const banIds=['U06KSSJFN']; //User ids to filter
    const useKittens=true; // use texture. if false, message blocks are removed seamlessly
    const kittenTextureUrl='https://d2gg9evh47fn9z.cloudfront.net/800px_COLOURBOX22766112.jpg'; //texture to replace messages
    const trackingLink=(id)=>`<a data-message-sender="${id}"/>`;
    let removeNodes=[];
    const replaceNodes=(node, threads=false)=>{
        let messageSender, messageCount=0;
        let elementArray=Array.from(node.querySelectorAll("div.c-virtual_list__item"));
        if (threads)
            elementArray=elementArray.filter(el=>/threads_view_[A-Z0-9]+/.test(el.id));
        elementArray.forEach(el=>{
            const l=el.querySelector('a[data-message-sender]');
        if (l)
            messageSender=l.getAttribute('data-message-sender');
        if (banIds.includes(messageSender)){
            messageCount++;
            if (useKittens){
                removeNodes.push(el);
            }
            else
            {
                el.innerHTML=trackingLink(messageSender);
            }
        }
            else if (useKittens && removeNodes.length){
                const offsetHeight=removeNodes.map(t=>t.offsetHeight||0).reduce((sum,t)=>sum+t,0);
                removeNodes.forEach((t,ix)=>{
                    if (ix===0)
                        t.innerHTML=`<div style='width:100%; height:${offsetHeight}px; background:url("${kittenTextureUrl}") top left;'>${trackingLink(messageSender)}</div>`;
                    else
                      t.innerHTML=trackingLink(messageSender);
                });
                removeNodes=[];
            }
        });
        return messageCount;
    };

    setInterval(()=>{
        const node=document.querySelector('div.c-message_list');
        let msgCount=0;
        if (node) {
            msgCount+=replaceNodes(node);
        }
        if (document.getElementById('threads_view'))
        {
            const msgCount=replaceNodes(document.getElementById('threads_view'),true);
        }
        if (msgCount) console.warn(msgCount +' messages filtered');
    },100);

})();