silverstripe-framework/admin/client/src/legacy/leaktools.js

import $ from 'jQuery';

var getHTML = function(el) {
  var clone = el.cloneNode(true);

  var div = $('<div></div>');
  div.append(clone);

  return div.html();
}

$.leaktools = {

  logDuplicateElements: function(){
    var els = $('*');
    var dirty = false;

    els.each(function(i, a){
      els.not(a).each(function(j, b){
        if (getHTML(a) == getHTML(b)) {
          dirty = true;
          console.log(a, b);
        }
      })
    })

    if (!dirty) console.log('No duplicates found');
  },

  logUncleanedElements: function(clean){
    $.each($.cache, function(){
      var source = this.handle && this.handle.elem;
      if (!source) return;

      var parent = source;
      while (parent && parent.nodeType == 1) parent = parent.parentNode;

      if (!parent) {
        console.log('Unattached', source);
        console.log(this.events);
        if (clean) $(source).unbind().remove();
      }
      else if (parent !== document) console.log('Attached, but to', parent, 'not our document', source);
    })
  }
};