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

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:149.0) Gecko/20100101 Firefox/149.0

Browser: Firefox 149

Operating system: Windows

Device Platform: Desktop

Date tested: one month ago

getElementsByClassname()[0]

3.2M/s

querySelector()

2.6M/s

querySelectorAll()[0]

112K/s

View exact numbers

Test name	Executions per second
✓ getElementsByClassname()[0]	3,233,479 Ops/sec
querySelector()	2,612,339 Ops/sec
querySelectorAll()[0]	111,915 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];