Implement '/t(ranslate)' command

Usage: /t [Whatever]
       or /translate [Whatever]

- Translate the 'whatever' and show the result in any kind of chatroom.
  Also, if the given '/t' message is a reply to another message,
  translate the reply target message as well.

@@ -112,3 +112,28 @@ bot.onText(/^(?!\/)((.|\n)+)/, (msg, match) => {
 
   translate(received_msg, chatId);
 });
+
+// /t(ranslate) [Whatever]
+// Translate the 'whatever' and show the result in any kind of chatroom.
+// Also, if the given '/t' message is a reply to another message,
+// translate the reply target message as well.
+bot.onText(/^\/(t|translate)($| ((.|\n)+))/, (msg, match) => {
+  const chatId = msg.chat.id;
+  const chatType = msg.chat.type;
+  const received_msg = match[3];
+  // Whether the given '/t' message is a reply to another message
+  const isReply = msg.reply_to_message != undefined;
+  // Whether a message has been given after '/t' command
+  const msgExists = received_msg != undefined;
+
+  // Translate the reply's target message
+  if (isReply) {
+    const replyMsg = msg.reply_to_message.text;
+    translate(replyMsg, chatId);
+  }
+
+  // Translate the message after '/t' if exists
+  if (msgExists) {
+    translate(received_msg, chatId);
+  }
+});