diff --git a/example/room-bot.ts b/example/room-bot.ts
index 6832e6625dbbaa58bcbedc5bbd784983a7226f55..5e667f8ee2d590859768d258cdedd08228d06e73 100644
--- a/example/room-bot.ts
+++ b/example/room-bot.ts
@@ -15,9 +15,9 @@
 /**
  *
  * create a room need at least three people
- * when we create a room, this is the 3rd people.
+ * when we create a room, the following one is the 3rd people.
  *
- * put name of one of your friend here, or create room will not work.
+ * put name of one of your friend here, or room create function will not work.
  *
  * ::::::::: ___CHANGE ME___ :::::::::
  *                           vvvvvvvvv
diff --git a/package.json b/package.json
index 01b2d2eb8a19c3ae8a499f4c52ced10fb16baa99..f57850c2d70bcdccb61ffe882297cc3b2115ad9d 100644
--- a/package.json
+++ b/package.json
@@ -93,6 +93,7 @@
     "arrify": "^1.0.1",
     "body-parser": "^1.15.2",
     "brolog": "^0.3.10",
+    "chromedriver": "^2.25.1",
     "express": "^4.13.4",
     "is-ci": "^1.0.9",
     "ps-tree": "^1.0.1",
diff --git a/script/docker.sh b/script/docker.sh
index a05b2298c02cb1c13de3a7e86406c2d48a767162..d28b0558e34f1cd070df018f8e7402517bc41e80 100755
--- a/script/docker.sh
+++ b/script/docker.sh
@@ -28,12 +28,18 @@ case "$1" in
     ret=$?
     ;;
 
+  clean)
+    docker ps -a | grep Exited | awk '{print $1}' | xargs docker rm || true
+    docker images | grep none | awk '{print $3}' | xargs docker rmi
+    ;;
+
   *)
     echo docker run -ti "$optRm" -v /dev/shm:/dev/shm "$imageName" "$@"
     exec docker run -ti "$optRm" -v /dev/shm:/dev/shm "$imageName" "$@"
-    ret=$?
     ;;
 esac
 
-echo "ERROR: exec return $ret ???"
-exit $ret
+[ "$ret" -ne 0 ] && {
+  echo "ERROR: exec return $ret ???"
+  exit $ret
+}