diff --git a/examples/room-bot.ts b/examples/room-bot.ts
index 19c21d97dc04cc940680afa89d3facd208cf797a..e6f6fbb0655aaa9edbfaa2b25730f1d189a550bc 100644
--- a/examples/room-bot.ts
+++ b/examples/room-bot.ts
@@ -121,28 +121,33 @@ bot
 /**
  * Global Event: room-join
  */
-.on('room-join', async function(this, room, inviteeList, inviter) {
+.on('room-join', async function(room, inviteeList, inviter) {
   log.info( 'Bot', 'EVENT: room-join - Room %s got new member %s, invited by %s',
             await room.topic(),
             inviteeList.map(c => c.name()).join(','),
             inviter.name(),
           )
+  const topic = await room.topic()
+  room.say(`welcome to ${topic}!`, inviteeList[0])
 })
 
 /**
  * Global Event: room-leave
  */
-.on('room-leave', async function(this, room, leaverList) {
+.on('room-leave', async function(room, leaverList) {
   log.info('Bot', 'EVENT: room-leave - Room %s lost member %s',
                   await room.topic(),
                   leaverList.map(c => c.name()).join(','),
               )
+  const topic = await room.topic()
+  const name  = leaverList[0] ? leaverList[0].name() : 'no contact!'
+  room.say(`kick off ${name} from ${topic}!` )
 })
 
 /**
  * Global Event: room-topic
  */
-.on('room-topic', function(this, room, topic, oldTopic, changer) {
+.on('room-topic', function(room, topic, oldTopic, changer) {
   try {
     log.info('Bot', 'EVENT: room-topic - Room %s change topic from %s to %s by member %s',
                     room,
@@ -150,6 +155,7 @@ bot
                     topic,
                     changer,
                 )
+    room.say(`room-topic - change topic from ${oldTopic} to ${topic} by member ${changer.name()}` )
   } catch (e) {
     log.error('Bot', 'room-topic event exception: %s', e.stack)
   }
@@ -380,6 +386,7 @@ async function createDingRoom(contact: Contact): Promise<any> {
 
     if (!helperContact) {
       log.warn('Bot', 'getHelperContact() found nobody')
+      contact.say(`You don't have a friend called ${HELPER_CONTACT_NAME}, because create a new room at least need 3 contacts, please set [HELPER_CONTACT_NAME] in the code first!`)
       return
     }
 
diff --git a/src/room.ts b/src/room.ts
index 5a9dda3c0e31eb3e0b8ec934f200b86d43404d87..3ed4ea55ca7d8ab198681f0e11715f78d604c8f2 100644
--- a/src/room.ts
+++ b/src/room.ts
@@ -318,7 +318,7 @@ export class Room extends Accessory implements Sayable {
       }
       await this.puppet.messageSendText({
         roomId: this.id,
-        contactId: replyToList[0].id,
+        contactId: (replyToList && replyToList.length && replyToList[0].id) || undefined,
       }, text)
     } else if (textOrContactOrFile instanceof FileBox) {
       await this.puppet.messageSendFile({