Run results for: tagName.toLowerCase() vs instanceof

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 17_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.6 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 17

Operating system: iOS 17.6.1

Device Platform: Mobile

Date tested: one year ago

localName

5.5M/s

tagName.toLowerCase()

4.9M/s

nodeName.toLowerCase()

4.8M/s

instanceof

4.8M/s

__proto__

4.2M/s

View exact numbers

Test name	Executions per second
✓ localName	5,514,098 Ops/sec
tagName.toLowerCase()	4,931,886 Ops/sec
nodeName.toLowerCase()	4,835,761 Ops/sec
instanceof	4,824,314 Ops/sec
__proto__	4,166,983 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.toLowerCase()
n += (xs[(Math.random() * 1000)|0].tagName.toLowerCase() === `div`)|0;
nodeName.toLowerCase()
n += (xs[(Math.random() * 1000)|0].nodeName.toLowerCase() === `div`)|0;
localName
n += (xs[(Math.random() * 1000)|0].localName === `div`)|0;
__proto__
n += ((xs[(Math.random() * 1000)|0]).__proto__ === HTMLDivElement.prototype)|0;