Run results for: String head vs legit head

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:48.0) Gecko/20100101 Firefox/48.0

Browser: Firefox 48

Operating system: Windows

Device Platform: Other

Date tested: 7 years ago

Test name	Executions per second
String selector	292190.3 Ops/sec
No selector	1231336.0 Ops/sec

HTML Preparation code:

<script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.1.0.min.js"></script>

Script Preparation code:

//Add 100,000 elements
var frag = document.createDocumentFragment();
for (var i=0; i<10; i++){
  var outDiv = document.createElement('div');
  for (var j=0; j<100; j++){
    var midDiv = document.createElement('div');
    for (var k=0; k<100; k++){
      var inDiv = document.createElement('div');
      if(i==6 && j==60){
        if(k==60)
          inDiv.id="one";
        else if(k==61)
          inDiv.id="two";
      }
      midDiv.appendChild(inDiv)
    }
    outDiv.appendChild(midDiv)
  }
  frag.appendChild(outDiv);
}
document.body.appendChild(frag);

Tests:

String selector
if ($("head").length != 1) throw Error();
No selector
if ($(document.head).length != 1) throw Error();

Run results for: String head vs legit head

String selector

No selector