diff --git a/core/src/scalive/HtmlElement.scala b/core/src/scalive/HtmlElement.scala
index 9ccb1ba..ea0d485 100644
--- a/core/src/scalive/HtmlElement.scala
+++ b/core/src/scalive/HtmlElement.scala
@@ -64,10 +64,10 @@ class HtmlAttr[V](val name: String, val codec: Codec[V, String]):
 
 class HtmlAttrJsonValue(val name: String):
 
-  def :=[V: JsonCodec](value: V): Mod.Attr =
+  def :=[V: JsonEncoder](value: V): Mod.Attr =
     Mod.Attr.Static(name, value.toJson, isJson = true)
 
-  def :=[V: JsonCodec](value: Dyn[V]): Mod.Attr =
+  def :=[V: JsonEncoder](value: Dyn[V]): Mod.Attr =
     Mod.Attr.Dyn(name, value(_.toJson), isJson = true)
 
 sealed trait Mod
diff --git a/core/src/scalive/JS.scala b/core/src/scalive/JS.scala
new file mode 100644
index 0000000..fed1f4b
--- /dev/null
+++ b/core/src/scalive/JS.scala
@@ -0,0 +1,53 @@
+package scalive
+
+import zio.json.*
+import zio.json.ast.Json
+
+val JS: JSCommands.JSCommand = JSCommands.empty
+
+object JSCommands:
+  opaque type JSCommand = List[Json]
+
+  def empty: JSCommand = List.empty
+
+  object JSCommand:
+    given JsonEncoder[JSCommand] =
+      JsonEncoder[Json].contramap(ops => Json.Arr(ops.reverse*))
+
+  private def classNames(names: String) = names.split("\\s+")
+
+  extension (ops: JSCommand)
+    private def addOp[A: JsonEncoder](kind: String, args: A) =
+      (kind, args).toJsonAST.getOrElse(throw new IllegalArgumentException()) :: ops
+
+    def toggleClass(
+      names: String,
+      to: String = "",
+      transition: String | (String, String, String) = "",
+      time: Int = 200,
+      blocking: Boolean = true
+    ) =
+      ops.addOp(
+        "toggle_class",
+        Args.ToggleClass(
+          classNames(names),
+          Some(to).filterNot(_.isBlank),
+          transition match
+            case ""                          => None
+            case names: String               => Some(classNames(names))
+            case t: (String, String, String) => Some(t.toList),
+          Some(time).filterNot(_ == 200),
+          Some(blocking).filterNot(_ == true)
+        )
+      )
+
+  private object Args:
+    final case class ToggleClass(
+      names: Seq[String],
+      to: Option[String],
+      transition: Option[Seq[String]],
+      time: Option[Int],
+      blocking: Option[Boolean])
+        derives JsonEncoder
+
+end JSCommands
diff --git a/example/src/HomeLiveView.scala b/example/src/HomeLiveView.scala
index 7b5f984..241f02a 100644
--- a/example/src/HomeLiveView.scala
+++ b/example/src/HomeLiveView.scala
@@ -4,8 +4,8 @@ import zio.stream.ZStream
 
 class HomeLiveView() extends LiveView[String, Unit]:
   val links = List(
-    "/counter" -> "Counter",
-    "/list"    -> "List"
+    "/counter"     -> "Counter",
+    "/list?q=test" -> "List"
   )
 
   def init = ZIO.succeed(())
diff --git a/example/src/ListLiveView.scala b/example/src/ListLiveView.scala
index 9beb8d8..6d92063 100644
--- a/example/src/ListLiveView.scala
+++ b/example/src/ListLiveView.scala
@@ -54,7 +54,11 @@ class ListLiveView(someParam: String) extends LiveView[Msg, Model]:
           phx.click := Msg.IncAge(1),
           "Inc age"
         ),
-        span(cls := "grow")
+        span(cls := "grow"),
+        button(
+          phx.click := JS.toggleClass("bg-red-500 border-5"),
+          "Toggle color"
+        )
       )
     )