IFTTT recently launch a pro plan with Filters support and advanced applets.
in this simple tutorial, will show you how to use Filters and write javascript code to receive a notification when a specific user tweet contains a specific keyword.

Filter Code :

let str=Twitter.newTweetByUser.Text;
let searchTerms=[
  "Facebook",
  "Bitcoin",
  "Amazon",
  "Tiktok"
]

let foundOne=0;
if(searchTerms.some(function(v){return str.indexOf(v)>=0;})){
  foundOne=1;
}

if(foundOne==0){
  IfNotifications.sendNotification.skip();
}