add alphanumeric function

sanitize.go

@@ -6,6 +6,7 @@ import (
 	"html"
 	"html/template"
 	"io"
+	"log"
 	"path"
 	"regexp"
 	"strings"
@@ -305,6 +306,19 @@ func Accents(s string) string {
 	return b.String()
 }
 
+// Get alphanumeric strings only
+func Alphanumeric(s string) string {
+
+	// Make a Regex to say we only want
+	reg, err := regexp.Compile("[^a-zA-Z0-9]+")
+	if err != nil {
+		log.Fatal(err)
+	}
+	processedString := reg.ReplaceAllString(s, "")
+
+	return processedString
+}
+
 var (
 	// If the attribute contains data: or javascript: anywhere, ignore it
 	// we don't allow this in attributes as it is so frequently used for xss

sanitize_test.go

@@ -234,3 +234,29 @@ func BenchmarkHTMLAllowed(b *testing.B) {
 		}
 	}
 }
+
+var alphanumerics = []Test{
+	{"#$ferf*", "ferf"},
+	{"aall$%", "aall"},
+	{"EFFFG^&", "EFFFG"},
+}
+
+func TestAlphanumeric(t *testing.T) {
+	for _, test := range alphanumerics {
+		output := Alphanumeric(test.input)
+		if output != test.expected {
+			t.Fatalf(Format, test.input, test.expected, output)
+		}
+	}
+}
+
+func BenchmarkAlphanumeric(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range alphanumerics {
+			output := Alphanumeric(test.input)
+			if output != test.expected {
+				b.Fatalf(Format, test.input, test.expected, output)
+			}
+		}
+	}
+}