TIL: document.querySelectorAll returns a NodeList
Modern browsers have the native selector engine document.querySelectorAll which is really useful for easily finding elements. I had assumed that it returned an Array but I've just found out that I was wrong and it returns a NodeList.
A NodeList is still a collection, but it doesn't have the Array prototype methods such as .filter or .map. You can convert the NodeList to an array using Array.from() or you can use items from the Array prototype using .call like this:
var elements = document.querySelectorAll(".content__article");
elements = [].filter.call(elements, function (el) {
// Your filter code goes here
});
