diff --git a/paths/paths_js.go b/paths/paths_js.go
new file mode 100644
index 000000000..1908254e7
--- /dev/null
+++ b/paths/paths_js.go
@@ -0,0 +1,9 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package paths
+
+func ensureStateDirPerms(dirPath string) error {
+	return nil
+}
diff --git a/paths/paths_unix.go b/paths/paths_unix.go
index fa95c783e..269abea0e 100644
--- a/paths/paths_unix.go
+++ b/paths/paths_unix.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !windows
-// +build !windows
+//go:build !windows && !js
+// +build !windows,!js
 
 package paths
 
diff --git a/portlist/portlist_js.go b/portlist/portlist_js.go
new file mode 100644
index 000000000..6e6b18ed2
--- /dev/null
+++ b/portlist/portlist_js.go
@@ -0,0 +1,17 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package portlist
+
+import "time"
+
+const pollInterval = 365 * 24 * time.Hour
+
+func listPorts() (List, error) {
+	return nil, nil
+}
+
+func addProcesses(pl []Port) ([]Port, error) {
+	return pl, nil
+}
diff --git a/portlist/portlist_other.go b/portlist/portlist_other.go
index 84193f623..f18a95d2c 100644
--- a/portlist/portlist_other.go
+++ b/portlist/portlist_other.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !linux && !windows && !darwin
-// +build !linux,!windows,!darwin
+//go:build !linux && !windows && !darwin && !js
+// +build !linux,!windows,!darwin,!js
 
 package portlist
 
diff --git a/types/logger/rusage_windows.go b/types/logger/rusage_stub.go
similarity index 86%
rename from types/logger/rusage_windows.go
rename to types/logger/rusage_stub.go
index ec5cf5513..3a9202d1c 100644
--- a/types/logger/rusage_windows.go
+++ b/types/logger/rusage_stub.go
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows || js
+// +build windows js
+
 package logger
 
 func rusageMaxRSS() float64 {
diff --git a/types/logger/rusage_nowindows.go b/types/logger/rusage_syscall.go
similarity index 92%
rename from types/logger/rusage_nowindows.go
rename to types/logger/rusage_syscall.go
index bb82bab88..b767718ac 100644
--- a/types/logger/rusage_nowindows.go
+++ b/types/logger/rusage_syscall.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !windows
-// +build !windows
+//go:build !windows && !js
+// +build !windows,!js
 
 package logger
 
diff --git a/wgengine/router/router_default.go b/wgengine/router/router_default.go
index 4e6a724ba..9f2e9aa46 100644
--- a/wgengine/router/router_default.go
+++ b/wgengine/router/router_default.go
@@ -16,8 +16,8 @@ import (
 	"tailscale.com/wgengine/monitor"
 )
 
-func newUserspaceRouter(logf logger.Logf, tunname string, tunDev tun.Device, linkMon *monitor.Mon) Router {
-	panic(fmt.Sprintf("unsupported OS %q", runtime.GOOS))
+func newUserspaceRouter(logf logger.Logf, tunDev tun.Device, linkMon *monitor.Mon) (Router, error) {
+	return nil, fmt.Errorf("unsupported OS %q", runtime.GOOS)
 }
 
 func cleanup(logf logger.Logf, interfaceName string) {