How can I detect whether a website has a drag and drop file upload functionality? With above code, I am getting all of the event listeners and if see the related event listeners such as drop, drag. However, it only checks the current page of the web application.

For example, I am not seeing drop event listener in the www.stackoverflow.com. However, https://stackoverflow.com/questions/ask has 'drop' event listener.

Array.from(document.querySelectorAll('*'))
  .reduce(function(pre, dom){
    var evtObj = getEventListeners(dom)
    Object.keys(evtObj).forEach(function (evt) {
      if (typeof pre[evt] === 'undefined') {
        pre[evt] = 0
      }
      pre[evt] += evtObj[evt].length
    })
    return pre
  }, {})

Is there any way to check the all of the event listeners accross different pages of the single web application?