Hendel SignalR Hub Methods in client side (js file)

Question

Iam using SignalR to create my first chat App every thing goes well but the problem is when I want to send message from one client to another not to all clients the question is how can I target just one client by its connection id or user name ?

this is My server side code (Hub class) i just want to know how to handel these methods in js to specify any client i want to send message to

        public async Task SendMessageUser(string user, string message)
        {
            // here you need to set a specifc the user 
            await Clients.User("username").SendAsync("ReceiveMessage", user, message);
        }

        public async Task SendMessageToClient(string user, string receiverConnectionId, string message)
        {

            await Clients.Client(receiverConnectionId).SendAsync("ReceiveMessage", user, message);
        }
        public async Task SendMessageUsers(string user, string message)
        {
            // here you need to set the list of Users
            await Clients.Users(new string[] { "myUser", "myUser2" }).SendAsync("ReceiveMessage", user, message);
        }