Run results for: ownerDocument.defaultView vs window.getComputedStyle

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.142 Safari/537.36

Browser: Chrome 75

Operating system: Mac OS X 10.13.1

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
ownerDocument.defaultView	1022947.0 Ops/sec
window.getComputedStyle	1370487.0 Ops/sec

HTML Preparation code:

<div id="root"><div>

Script Preparation code:

var el = document.getElementById("root");
function getStyle(elem){
  var view = elem.ownerDocument.defaultView;
  if ( !view || !view.opener ) {
    view = window;
  }

  return view.getComputedStyle( elem );
}

function getStyle2(elem){
  return window.getComputedStyle( elem );
}

Tests:

ownerDocument.defaultView
var computedStyle = getStyle(el);
window.getComputedStyle
var computedStyle = getStyle2(el);