A-simple-way-to-check-if-a-whatapp-contact-is-online

self explanatory name

1. go to web.whatsapp.com
2. open the chat of the person you want to check
3. press F12 or inspect element
4. press on console
5. paste following code:

last_title = document.getElementsByClassName("O90ur _3FXB1")[0].title;
while(true){
    await new Promise(r => setTimeout(r, 1000));
    if (document.getElementsByClassName("O90ur _3FXB1")[0].title != last_title){
        window.location.href = "https://www.youtube.com/watch?v=dQw4w9WgXcQ";
    }
}

6. press Enter
7. stay on the same tab (you'll appear online!)
8. when the person logs, a song will start playing NOTE - check it out first on a friend's phone