A JS snippet for highlighting tweets with lots of RTs or hearts

highlight_tweets.js

(function(){
  'use strict';   
    
  let cap = 100; // 100+ RTs or hearts produces max yellow bg color
      
  $('.tweet', '.stream-items').each((i, tweet) => {
    let all_nums = $(tweet)
        .find('.ProfileTweet-actionList .ProfileTweet-actionCount:visible')
        .map((j, elem) => Number(elem.textContent)).toArray();
     
    let num = Math.min(Math.max.apply(Math, all_nums.concat(0)), cap);    
    let str = Math.floor(255 * (1 - num/cap)).toString(16);
    if (str.length === 1) str = '0' + str;
      
    $(tweet).css({ 'background-color': '#FFFF' + str });    
  });    
}());

Cache the $(tweet) you're calling it twice in line #7 and #17

And you only need one find(): $(tweet).find('.ProfileTweet-actionList .ProfileTweet-actionCount:visible')

Caching $(foo) is a micro-optimization. It only takes about 5 microseconds, so you can have dozens of them in a code block without affecting performance.

I’ve switched to one .find(); seems to work fine.