fix(core): only unset dom prop when not present

yyx990803 · yyx990803 · commit f11449d916a4 · 2019-03-20T14:13:23.000+08:00
fix vuejs#9650
diff --git a/src/platforms/web/runtime/modules/dom-props.js b/src/platforms/web/runtime/modules/dom-props.js
@@ -19,10 +19,11 @@ function updateDOMProps (oldVnode: VNodeWithData, vnode: VNodeWithData) {
   }
 
   for (key in oldProps) {
-    if (isUndef(props[key])) {
+    if (!(key in props)) {
       elm[key] = ''
     }
   }
+
   for (key in props) {
     cur = props[key]
     // ignore children if the node has textContent or innerHTML,

Original file line number	Diff line number	Diff line change
`@@ -19,10 +19,11 @@ function updateDOMProps (oldVnode: VNodeWithData, vnode: VNodeWithData) {`
`19`	`19`	`}`
`20`	`20`
`21`	`21`	`for (key in oldProps) {`
`22`		`- if (isUndef(props[key])) {`
	`22`	`+ if (!(key in props)) {`
`23`	`23`	`elm[key] = ''`
`24`	`24`	`}`
`25`	`25`	`}`
	`26`	`+`
`26`	`27`	`for (key in props) {`
`27`	`28`	`cur = props[key]`
`28`	`29`	`// ignore children if the node has textContent or innerHTML,`