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

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:145.0) Gecko/20100101 Firefox/145.0

Browser: Firefox 145

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 8 months ago

classList.contains

908/s

className.indexOf

506/s

View exact numbers

Test name	Executions per second
✓ classList.contains	908 Ops/sec
className.indexOf	506 Ops/sec

HTML Preparation code:

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

Tests:

className.indexOf
var element = document.getElementById("foo"); var i = 1000000; while (i--) { if (element.className.indexOf("test") !== -1) {} }
classList.contains
var element = document.getElementById("foo"); var i = 1000000; while (i--) { element.classList.contains("test"); }