diff --git a/property.go b/property.go
index 98e895e..beabc5d 100644
--- a/property.go
+++ b/property.go
@@ -1,13 +1,12 @@
 package goquery
 
 import (
-	"regexp"
 	"strings"
 
 	"golang.org/x/net/html"
 )
 
-var rxClassTrim = regexp.MustCompile("[\t\r\n]")
+var classTrimReplacer = strings.NewReplacer("\t", " ", "\r", " ", "\n", " ")
 
 // Attr gets the specified attribute's value for the first element in the
 // Selection. To get the value for each element individually, use a looping
@@ -140,9 +139,14 @@ func (s *Selection) AddClass(class ...string) *Selection {
 func (s *Selection) HasClass(class string) bool {
 	class = " " + class + " "
 	for _, n := range s.Nodes {
-		classes, _ := getClassesAndAttr(n, false)
-		if strings.Contains(classes, class) {
-			return true
+		if n.Type != html.ElementNode {
+			continue
+		}
+		if attr := getAttributePtr("class", n); attr != nil {
+			val := classTrimReplacer.Replace(attr.Val)
+			if strings.Contains(" "+val+" ", class) {
+				return true
+			}
 		}
 	}
 	return false
@@ -243,10 +247,8 @@ func getClassesAndAttr(n *html.Node, create bool) (classes string, attr *html.At
 
 	if attr == nil {
 		classes = " "
-	} else if strings.ContainsAny(attr.Val, "\t\r\n") {
-		classes = rxClassTrim.ReplaceAllString(" "+attr.Val+" ", " ")
 	} else {
-		classes = " " + attr.Val + " "
+		classes = classTrimReplacer.Replace(" " + attr.Val + " ")
 	}
 
 	return
diff --git a/query.go b/query.go
index fe86bf0..293afeb 100644
--- a/query.go
+++ b/query.go
@@ -24,19 +24,32 @@ func (s *Selection) IsMatcher(m Matcher) bool {
 // IsFunction checks the current matched set of elements against a predicate and
 // returns true if at least one of these elements matches.
 func (s *Selection) IsFunction(f func(int, *Selection) bool) bool {
-	return s.FilterFunction(f).Length() > 0
+	for i, n := range s.Nodes {
+		if f(i, newSingleSelection(n, s.document)) {
+			return true
+		}
+	}
+	return false
 }
 
 // IsSelection checks the current matched set of elements against a Selection object
 // and returns true if at least one of these elements matches.
 func (s *Selection) IsSelection(sel *Selection) bool {
-	return s.FilterSelection(sel).Length() > 0
+	if sel == nil {
+		return false
+	}
+	return s.IsNodes(sel.Nodes...)
 }
 
 // IsNodes checks the current matched set of elements against the specified nodes
 // and returns true if at least one of these elements matches.
 func (s *Selection) IsNodes(nodes ...*html.Node) bool {
-	return s.FilterNodes(nodes...).Length() > 0
+	for _, n := range s.Nodes {
+		if isInSlice(nodes, n) {
+			return true
+		}
+	}
+	return false
 }
 
 // Contains returns true if the specified Node is within,
diff --git a/traversal.go b/traversal.go
index c45fa5d..46bac05 100644
--- a/traversal.go
+++ b/traversal.go
@@ -562,13 +562,12 @@ func findWithMatcher(nodes []*html.Node, m Matcher) []*html.Node {
 func getParentsNodes(nodes []*html.Node, stopm Matcher, stopNodes []*html.Node) []*html.Node {
 	return mapNodes(nodes, func(i int, n *html.Node) (result []*html.Node) {
 		for p := n.Parent; p != nil; p = p.Parent {
-			sel := newSingleSelection(p, nil)
 			if stopm != nil {
-				if sel.IsMatcher(stopm) {
+				if stopm.Match(p) {
 					break
 				}
 			} else if len(stopNodes) > 0 {
-				if sel.IsNodes(stopNodes...) {
+				if isInSlice(stopNodes, p) {
 					break
 				}
 			}
@@ -589,13 +588,9 @@ func getSiblingNodes(nodes []*html.Node, st siblingType, untilm Matcher, untilNo
 	if st == siblingNextUntil || st == siblingPrevUntil {
 		f = func(n *html.Node) bool {
 			if untilm != nil {
-				// Matcher-based condition
-				sel := newSingleSelection(n, nil)
-				return sel.IsMatcher(untilm)
+				return untilm.Match(n)
 			} else if len(untilNodes) > 0 {
-				// Nodes-based condition
-				sel := newSingleSelection(n, nil)
-				return sel.IsNodes(untilNodes...)
+				return isInSlice(untilNodes, n)
 			}
 			return false
 		}