Creating a toast notification system

So rn im creating what i said in the past devlog about a toast navigation. This isnt finished yet, im still figuring out an way to check the end of the timer, i found some ways to do it, like using an simple if inside the countdown. I didnt comment but i am using an setInterval to decrease the time and an <progress> tag to show the value

but that is a bad ideia, imagine doing 1 if every 50 ms? that dont cost a lot of processing power, but i still will search for other ways to do it just to check, if yall got any hints or ideas leave a comment.
Also i will improve the design, the design is petty poor.