Run results for: <br> vs display:block;

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36

Browser: Chrome 91

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
<br>	1889.2 Ops/sec
display:block;	988.7 Ops/sec

Script Preparation code:

function textNodesUnder(el){
  var n, a=[], walk=document.createTreeWalker(el,NodeFilter.SHOW_TEXT,null,false);
  while(n=walk.nextNode()) a.push(n);
  return a;
}

function textNodeMapper(help = ['p','code',"span"]){
	textNodesUnder(document.body).map(function(e){
		if (!/\w/.test(e.data)){return ""}
		return help.map(function(lol){
			if (e.parentElement.localName === lol){ return e.data}
			if (e.id === lol){ return e.data}
			if (e.parentElement.className === lol){ return e.data}
			return null
		}).toString()
	}).filter(Boolean)
}


	var starterPack = 	["P",'SECTION',"SPAN","CODE","DIV"
						,"A","DT","DL","DD","FOOTER","MENU"]


if (localStorage.getItem('name2kill') === null){
	localStorage.setItem('name2kill',JSON.stringify(starterPack));
}


var tableEle, trEle, thEle;
tableEle = document.createElement('table');
trEle = document.createElement('tr');
thEle = document.createElement('th');
		tableEle.id = "tableEle";
	//	tableEle.style = "display:block;";
trEle.appendChild(thEle);
tableEle.appendChild(trEle);

var addEle;
addEle = document.createElement('button');
		addEle.id = "addEle";
addEle.appendChild(document.createTextNode('add-tag,class,id-name'));
//addEle.addEventListener("click", addKill);
addEle.type = "button";

var removeEle;
removeEle = document.createElement('button');
		removeEle.id = "removeEle";
removeEle.appendChild(document.createTextNode('unlist'));
//removeEle.addEventListener("click", removeKill);
removeEle.type = "button";

var resetEle;
resetEle = document.createElement('button');
		resetEle.id = "resetEle";
resetEle.appendChild(document.createTextNode('clearlist'));
//resetEle.addEventListener("click", killStorage);
resetEle.type = "button";

var inputEle;
inputEle = document.createElement('input');
		inputEle.id = "inputEle";
inputEle.value = '';
inputEle.type = "text";
//inputEle.setAttribute('style', 'width: initial;');

var divEle;
divEle = document.createElement("div");
	divEle.id = "divEle";
divEle.setAttribute('style', "top: 0; right: 0; position: fixed; z-index: 2146;");

var checkExist = setInterval(function() {
	if (document.body) { clearInterval(checkExist);
		divEle.appendChild(inputEle);
		divEle.appendChild(addEle);
		divEle.appendChild(removeEle);
		divEle.appendChild(resetEle);
	//	divEle.appendChild(document.createElement('br'));
	//	tableEle.style = "display:block;";
	//	divEle.appendChild(tableEle);
	//	document.body.appendChild(divEle);
	}
}, 100);

Tests:

<br>
divEle.appendChild(document.createElement('br')); // tableEle.style = "display:block;"; divEle.appendChild(tableEle); document.body.appendChild(divEle);
display:block;
// divEle.appendChild(document.createElement('br')); tableEle.style = "display:block;"; divEle.appendChild(tableEle); document.body.appendChild(divEle);

Run results for: <br> vs display:block;

javascript generated Elements, when newline an Element <br> vs display:block; performance check

<br>

display:block;