sample_wasm.go

func sendMessage(_ js.Value, _ []js.Value) interface{} {
	doc := js.Global().Get("document")
	msg := doc.Call("getElementById", "message").Get("value").String()
	user := doc.Call("getElementById", "username").Get("value").String()
	doc.Call("getElementById", "message").Set("value", "")
	println(user, msg)

	location := js.Global().Get("window").Get("location")
	scheme := "ws"
	if location.Get("protocol").String() == "https:" {
		scheme = "wss"
	}
	host := location.Get("host").String()
	addr := fmt.Sprintf("%s://%s/ws",scheme, host)
	fmt.Printf("Connecting to %s", addr)
	ws := js.Global().Get("WebSocket").New(addr)
	ws.Call("addEventListener", "open", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		ws.Call("send", fmt.Sprintf("%s - %s", user, msg))
		return nil
	}))
	return nil
}