Add event when all button clicked

I'm working on an app to calm panic attacks. I'm using the 5-4-3-2-1 method, the user has to identify 5 things he sees, 4 things he hears and so on. Each time he identifies something he has to click a button. What I want to do is when, for the first step, when all 5 buttons are clicked, then the method goes on to the next step with four buttons and so on.

I can try and do it with flowrouter instead of coding it, but coding the whole method in one file would make it easier to insert it in the app.

<div class="container"> <button class="btn" id="btn1">1</button> </div>