Run results for: className.indexOf vs. classList.contains

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/119.0

Browser: Firefox 119

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 2 years ago

className

2.1M/s

classList

1.2M/s

View exact numbers

Test name	Executions per second
✓ className	2,119,358 Ops/sec
classList	1,205,775 Ops/sec

HTML Preparation code:

<div id="foo" class="test"></div>

Tests:

className
var element = document.getElementById("foo"); var i = 1000; while (i--) { if (element.className.indexOf("test") !== -1) {} }
classList
var element = document.getElementById("foo"); var i = 1000; while (i--) { element.classList.contains("test"); }