What is the universal "Add to cart" selecter on ALL shopify stores?

Shopify Partner
32 0 4

I created an app which imports some Javascript to the store front. This javascript code has a click event for the "Add to cart" button.

some stores have the class "add-to-cart" but others don't. So right now i have $(".add-to-cart").click(function(){..........}). This click event fires on some stores with that class and doesn't fire on others.

Is there a universal id or class or selector that ALL stores use so that the click event will fire on every store?