From 95a9282b20ed963a329fa4ecf9f6f96929308290 Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Tue, 19 Apr 2016 11:07:57 -0400
Subject: [PATCH] early return in vdom update modules

---
 src/runtime/dom-backend/modules/attrs.js  | 3 +++
 src/runtime/dom-backend/modules/events.js | 3 +++
 src/runtime/dom-backend/modules/props.js  | 3 +++
 src/runtime/dom-backend/modules/style.js  | 3 +++
 4 files changed, 12 insertions(+)

diff --git a/src/runtime/dom-backend/modules/attrs.js b/src/runtime/dom-backend/modules/attrs.js
index a6a84d6a..d71832f4 100644
--- a/src/runtime/dom-backend/modules/attrs.js
+++ b/src/runtime/dom-backend/modules/attrs.js
@@ -14,6 +14,9 @@ const xlinkNS = 'http://www.w3.org/1999/xlink'
 const isXlink = name => name.slice(0, 6) === 'xlink:'
 
 function updateAttrs (oldVnode, vnode) {
+  if (!oldVnode.data.attrs && !vnode.data.attrs) {
+    return
+  }
   let key, cur, old
   const elm = vnode.elm
   const oldAttrs = oldVnode.data.attrs || {}
diff --git a/src/runtime/dom-backend/modules/events.js b/src/runtime/dom-backend/modules/events.js
index dc09e785..1db94f5d 100644
--- a/src/runtime/dom-backend/modules/events.js
+++ b/src/runtime/dom-backend/modules/events.js
@@ -1,6 +1,9 @@
 import { updateListeners } from '../../vdom/helpers'
 
 function updateDOMListeners (oldVnode, vnode) {
+  if (!oldVnode.data.on && !vnode.data.on) {
+    return
+  }
   const on = vnode.data.on
   const oldOn = oldVnode.data.on || {}
   updateListeners(on, oldOn, (event, handler, capture) => {
diff --git a/src/runtime/dom-backend/modules/props.js b/src/runtime/dom-backend/modules/props.js
index fe228af9..35ac7183 100644
--- a/src/runtime/dom-backend/modules/props.js
+++ b/src/runtime/dom-backend/modules/props.js
@@ -1,4 +1,7 @@
 function updateProps (oldVnode, vnode) {
+  if (!oldVnode.data.props && !vnode.data.props) {
+    return
+  }
   let key, cur, old
   const elm = vnode.elm
   const oldProps = oldVnode.data.props || {}
diff --git a/src/runtime/dom-backend/modules/style.js b/src/runtime/dom-backend/modules/style.js
index 2f9f38ed..34e7b473 100644
--- a/src/runtime/dom-backend/modules/style.js
+++ b/src/runtime/dom-backend/modules/style.js
@@ -29,6 +29,9 @@ function toObject (arr) {
 }
 
 function updateStyle (oldVnode, vnode) {
+  if (!oldVnode.data.style && !vnode.data.style) {
+    return
+  }
   let cur, name
   const elm = vnode.elm
   const oldStyle = oldVnode.data.style || {}