diff --git a/src/browser/html/window.zig b/src/browser/html/window.zig
index e41c18ad..0a8494b6 100644
--- a/src/browser/html/window.zig
+++ b/src/browser/html/window.zig
@@ -20,7 +20,7 @@ const std = @import("std");
 
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
-const Function = @import("../env.zig").Function;
+const Env = @import("../env.zig").Env;
 const Page = @import("../page.zig").Page;
 const Loop = @import("../../runtime/loop.zig").Loop;
 
@@ -36,6 +36,9 @@ const CSSStyleDeclaration = @import("../cssom/css_style_declaration.zig").CSSSty
 const Screen = @import("screen.zig").Screen;
 const Css = @import("../css/css.zig").Css;
 
+const Function = Env.Function;
+const JsObject = Env.JsObject;
+
 const storage = @import("../storage/storage.zig");
 
 // https://dom.spec.whatwg.org/#interface-window-extensions
@@ -184,13 +187,12 @@ pub const Window = struct {
         return page.loop.cancel(kv.value.loop_id);
     }
 
-    pub fn _setTimeout(self: *Window, cbk: Function, delay: ?u32, page: *Page) !u32 {
-        return self.createTimeout(cbk, delay, page, .{});
+    pub fn _setTimeout(self: *Window, cbk: Function, delay: ?u32, params: []Env.JsObject, page: *Page) !u32 {
+        return self.createTimeout(cbk, delay, page, .{ .args = params });
     }
 
-    // TODO handle callback arguments.
-    pub fn _setInterval(self: *Window, cbk: Function, delay: ?u32, page: *Page) !u32 {
-        return self.createTimeout(cbk, delay, page, .{ .repeat = true });
+    pub fn _setInterval(self: *Window, cbk: Function, delay: ?u32, params: []Env.JsObject, page: *Page) !u32 {
+        return self.createTimeout(cbk, delay, page, .{ .repeat = true, .args = params });
     }
 
     pub fn _clearTimeout(self: *Window, id: u32, page: *Page) !void {
@@ -230,10 +232,11 @@ pub const Window = struct {
     }
 
     const CreateTimeoutOpts = struct {
+        args: []Env.JsObject = &.{},
         repeat: bool = false,
         animation_frame: bool = false,
     };
-    fn createTimeout(self: *Window, cbk: Function, delay_: ?u32, page: *Page, comptime opts: CreateTimeoutOpts) !u32 {
+    fn createTimeout(self: *Window, cbk: Function, delay_: ?u32, page: *Page, opts: CreateTimeoutOpts) !u32 {
         const delay = delay_ orelse 0;
         if (delay > 5000) {
             log.warn(.user_script, "long timeout ignored", .{ .delay = delay, .interval = opts.repeat });
@@ -258,6 +261,15 @@ pub const Window = struct {
         }
         errdefer _ = self.timers.remove(timer_id);
 
+        const args = opts.args;
+        var persisted_args: []Env.JsObject = &.{};
+        if (args.len > 0) {
+            persisted_args = try page.arena.alloc(Env.JsObject, args.len);
+            for (args, persisted_args) |a, *ca| {
+                ca.* = try a.persist();
+            }
+        }
+
         const delay_ms: u63 = @as(u63, delay) * std.time.ns_per_ms;
         const callback = try arena.create(TimerCallback);
 
@@ -266,6 +278,7 @@ pub const Window = struct {
             .loop_id = 0, // we're going to set this to a real value shortly
             .window = self,
             .timer_id = timer_id,
+            .args = persisted_args,
             .node = .{ .func = TimerCallback.run },
             .repeat = if (opts.repeat) delay_ms else null,
             .animation_frame = opts.animation_frame,
@@ -344,6 +357,8 @@ const TimerCallback = struct {
 
     window: *Window,
 
+    args: []Env.JsObject = &.{},
+
     fn run(node: *Loop.CallbackNode, repeat_delay: *?u63) void {
         const self: *TimerCallback = @fieldParentPtr("node", node);
 
@@ -353,7 +368,7 @@ const TimerCallback = struct {
         if (self.animation_frame) {
             call = self.cbk.tryCall(void, .{self.window.performance._now()}, &result);
         } else {
-            call = self.cbk.tryCall(void, .{}, &result);
+            call = self.cbk.tryCall(void, self.args, &result);
         }
 
         call catch {
@@ -427,11 +442,17 @@ test "Browser.HTML.Window" {
         .{ "innerWidth", "2" },
     }, .{});
 
-    // cancelAnimationFrame should be able to cancel a request with the given id
     try runner.testCases(&.{
         .{ "let longCall = false;", null },
         .{ "window.setTimeout(() => {longCall = true}, 5001);", null },
         .{ "longCall;", "false" },
+
+        .{ "let wst = 0;", null },
+        .{ "window.setTimeout(() => {wst += 1}, 1)", null },
+        .{ "wst", "1" },
+
+        .{ "window.setTimeout((a, b) => {wst = a + b}, 1, 2, 3)", null },
+        .{ "wst", "5" },
     }, .{});
 
     // window event target
diff --git a/src/runtime/js.zig b/src/runtime/js.zig
index 789ca93e..b5216ab8 100644
--- a/src/runtime/js.zig
+++ b/src/runtime/js.zig
@@ -1766,13 +1766,28 @@ pub fn Env(comptime State: type, comptime WebApis: type) type {
                 const js_this = try js_context.valueToExistingObject(this);
 
                 const aargs = if (comptime @typeInfo(@TypeOf(args)) == .null) struct {}{} else args;
-                const fields = @typeInfo(@TypeOf(aargs)).@"struct".fields;
-                var js_args: [fields.len]v8.Value = undefined;
-                inline for (fields, 0..) |f, i| {
-                    js_args[i] = try js_context.zigValueToJs(@field(aargs, f.name));
-                }
 
-                const result = self.func.castToFunction().call(js_context.v8_context, js_this, &js_args);
+                const js_args: []const v8.Value = switch (@typeInfo(@TypeOf(aargs))) {
+                    .@"struct" => |s| blk: {
+                        const fields = s.fields;
+                        var js_args: [fields.len]v8.Value = undefined;
+                        inline for (fields, 0..) |f, i| {
+                            js_args[i] = try js_context.zigValueToJs(@field(aargs, f.name));
+                        }
+                        const cargs: [fields.len]v8.Value = js_args;
+                        break :blk &cargs;
+                    },
+                    .pointer => blk: {
+                        var values = try js_context.call_arena.alloc(v8.Value, args.len);
+                        for (args, 0..) |a, i| {
+                            values[i] = try js_context.zigValueToJs(a);
+                        }
+                        break :blk values;
+                    },
+                    else => @compileError("JS Function called with invalid paremter type"),
+                };
+
+                const result = self.func.castToFunction().call(js_context.v8_context, js_this, js_args);
                 if (result == null) {
                     return error.JSExecCallback;
                 }