Run results for: tagName vs instanceof

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:56.0) Gecko/20100101 Firefox/56.0

Browser: Firefox 56

Operating system: Mac OS X 10.11

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
instanceof	4646398.5 Ops/sec
tagName	3832789.0 Ops/sec
nodeName	4182275.8 Ops/sec
localName	3876922.2 Ops/sec
__proto__	7219520.5 Ops/sec

Script Preparation code:

var xs = [];
var n = 0;

for (let i = 0; i < 1000; ++i) {
  xs[i] = (Math.random() > .5) ? document.createElement(`div`) : document.createElement(`span`);
};

Tests:

instanceof
n += ((xs[(Math.random() * 1000)|0]) instanceof HTMLDivElement)|0;
tagName
n += (xs[(Math.random() * 1000)|0].tagName === `DIV`)|0;
nodeName
n += (xs[(Math.random() * 1000)|0].nodeName === `DIV`)|0;
localName
n += (xs[(Math.random() * 1000)|0].localName === `div`)|0;
__proto__
n += ((xs[(Math.random() * 1000)|0]).__proto__ === HTMLDivElement.prototype)|0;

Run results for: tagName vs instanceof

instanceof

tagName

nodeName

localName

__proto__

proto