Run results for: Getting first element using querySelector vs querySelectorAll vs getElementsByClassName

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser: Chrome 134

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

querySelector()

12.8M/s

getElementsByClassname()[0]

12.4M/s

querySelectorAll()[0]

235K/s

View exact numbers

Test name	Executions per second
✓ querySelector()	12,829,210 Ops/sec
getElementsByClassname()[0]	12,440,013 Ops/sec
querySelectorAll()[0]	235,434 Ops/sec

HTML Preparation code:

<div id="test-container"></div>

Script Preparation code:

{
const elementCount = 1000;
const container = window.container = document.getElementById('test-container');
const fragment = document.createDocumentFragment();
const entities = window.entities = [];

for (let i=0; i < elementCount; i++) {
	const element = document.createElement('div');
	element.classList.add(`test-${i%4}`);
	element.setAttribute(`test`, i%4);
 	fragment.append(element);
	entities.push(element);
}
container.append(fragment);
}

Tests:

querySelector()
const randomID = 0|Math.random()*4; const result = window.container.querySelector(`.test-${randomID}`);
querySelectorAll()[0]
const randomID = 0|Math.random()*4; const result = window.container.querySelectorAll(`.test-${randomID}`)[0];
getElementsByClassname()[0]
const randomID = 0|Math.random()*4; const result = window.container.getElementsByClassName(`test-${randomID}`)[0];