Action to be taken when an element with a specific class is clicked

getElementsByClassName returns HTMLCollection instead of a single element.
https://developer.mozilla.org/ja/docs/Web/API/Document/getElementsByClassName

because you must specify a target to click on getElementsByClassName("hoge-btn")[0] and other elements.
Or

varyments= document.getElementsByClassName('hoge-btn');
Array.prototype.forEach.call(elements, function(item){
  // processing using an item
  item.onclick=function(){
    window.alert('View Alerts');
  };
}

You must configure events for all elements, such as .

https://hacknote.jp/archives/21892/

Registering an event listener one by one is a pain in the neck, so you can use document to process the event.click The event starts the event listener for all the ancestor nodes unless stopPropagation().

 document.addEventListener('click', function(event){
  if(event.target.classList.contains('hoge-btn')}{
    alert('View Alerts');
  }
}, false);

This code can be executed at a time when there is no element in the document that has a hoge-btn class, but it can still handle the click of the element with the hoge-btn that you added later.