Run results for: className vs getAttribute('class') vs classList

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36

Browser: Chrome 100

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
get/set Attribute	1225.8 Ops/sec
+= className	535.6 Ops/sec
classList.add()	240410.7 Ops/sec

HTML Preparation code:

<div id="root" class="whopper w-screen h-screen bg-neutral-150 flex-row center">
  <div class="whiplash pos-rel w-500 min-h-full bg-neutral-250 flex-col overflow-hidden">
    <div class="whoop">
      <div class="wheep">
        <div class="whyne-stein pos-rel mg-x-200 mg-y-auto pd-500 bg-neutral-500 cursor-pointer">
          <span class="joker text-bold text-xl text-white bg-black pd-400 rounded-full">WHY SO SERIOUS?</span>
        </div>
      </div>
    </div>
  </div>
</div>

Script Preparation code:

function tagElementsByAttribute(children) {
	for (let i = 0, child, cls; i < children.length; i++) {
    	child = children[i];
      	child.setAttribute('class', child.getAttribute('class') + ' tagged');
     	if (child.firstElementChild) {
        	tagElementsByAttribute(child.children);
        }
    }
}

function tagElementsByClassName(children) {
	for (let i = 0, child, cls; i < children.length; i++) {
    	child = children[i];
      	child.className += ' tagged';
     	if (child.firstElementChild) {
        	tagElementsByClassName(child.children);
        }
    }
}

function tagElementsByClassList(children) {
	for (let i = 0, child, cls; i < children.length; i++) {
    	child = children[i];
     	child.classList.add('tagged');
     	if (child.firstElementChild) {
        	tagElementsByClassList(child.children);
        }
    }
}

Tests:

get/set Attribute
tagElementsByAttribute(document.getElementById('root').children);
+= className
tagElementsByClassName(document.getElementById('root').children);
classList.add()
tagElementsByClassList(document.getElementById('root').children);

Run results for: className vs getAttribute('class') vs classList

get/set Attribute

+= className

classList.add()