From 3b7149575734069bb7e2bd6f7e9164fe6fdf36ff Mon Sep 17 00:00:00 2001
From: jvoisin <julien.voisin@dustri.org>
Date: Wed, 27 May 2026 15:26:22 +0200
Subject: [PATCH] perf: pre-check raw class attribute in HasClass
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HasClass normalized every matching element's class attribute with
classTrimReplacer before checking for the target token, even when the
raw attribute value could not possibly contain that class at all.

Add a cheap strings.Contains(attr.Val, rawClass) pre-check and only run
the replacer on plausible matches. This preserves behavior for class
attributes containing tabs/newlines while skipping most of the work on
misses.

BenchmarkHasClass on arm64 over 10 runs:

name         old time/op   new time/op   delta
HasClass-8    9.809µs       2.660µs      -72.89% (p=0.000)
---
 property.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/property.go b/property.go
index beabc5d..ac8e471 100644
--- a/property.go
+++ b/property.go
@@ -137,12 +137,16 @@ func (s *Selection) AddClass(class ...string) *Selection {
 // HasClass determines whether any of the matched elements are assigned the
 // given class.
 func (s *Selection) HasClass(class string) bool {
+	rawClass := class
 	class = " " + class + " "
 	for _, n := range s.Nodes {
 		if n.Type != html.ElementNode {
 			continue
 		}
 		if attr := getAttributePtr("class", n); attr != nil {
+			if !strings.Contains(attr.Val, rawClass) {
+				continue
+			}
 			val := classTrimReplacer.Replace(attr.Val)
 			if strings.Contains(" "+val+" ", class) {
 				return true