Check if any element in a NodeList has a specific class using ES6

Array.from(document.getElementsByClassName("item")).some(({classList}) =>
   classList.contains('active'))

is probably the best ES6 can give you, which is essentially the same as your code above.

It has nothing to do with ES2015, but you can use document.querySelector() much like the basic jQuery API:

 var isActive = document.querySelector(".item.active") != null;

You don't really need ES6 to do the same thing in vanilla JS.

// jQuery
var isActive = $(".item").hasClass("active"); 

// Plain JavaScript
var isActive = document.querySelector('.item').classList.contains('active');