JQUERY，AJAX if else语句

Question

I try to make a simple chat bot. So far the bot answer is user type in defined question. But how can I make it that the chatbot gives out a "sorry I don't understand" if user ask something that is not defined?

function ai(message){
    if (username.length<3){
        username = message;
        send_message("Nice to meet you " + username + ", how are you today?");
        responsiveVoice.speak("Nice to meet you " + username + ", how are you today?");
    } 

    if (message.toLowerCase().indexOf("how are you")>=0){
        send_message("Thanks, Iam good!");
        responsiveVoice.speak("Thanks, Iam good!");
    }

    if (message.toLowerCase().indexOf("time")>=0){
        var date = new Date();
        var h = date.getHours();
        var m = date.getMinutes();
        send_message("Current time is "+h+":"+m);
    }

    if (message.toLowerCase().indexOf("thanks")>=0){
        send_message("You are welcome");
    }

    if (message.toLowerCase().indexOf("Thank you")>=0){
        send_message("No Problem");
    }

    if (message.toLowerCase().indexOf("thank you very much")>=0){
        send_message("Welcome Sir!");          
    } 
}

Answer 1

Use else?

if (message.toLowerCase().indexOf("how are you")>=0){
  send_message("Thanks, Iam good!");
  responsiveVoice.speak("Thanks, Iam good!");
} else {
  send_message("sorry I don't understand");
  responsiveVoice.speak("sorry I don't understand");
}

You can also use switch statement:

switch (message.toLowerCase()) {
  case "how are you":
    send_message("Thanks, Iam good!");
    responsiveVoice.speak("Thanks, Iam good!");
    break;
  case "something else":
    send_message("something else");
    responsiveVoice.speak("something else");
    break;
  default:
    send_message("sorry I don't understand");
    responsiveVoice.speak("sorry I don't understand");
}