refactor: option merging + extract helper functions

packages/renderer-dom/src/index.ts

@@ -1,4 +1,4 @@
-import { createRenderer, VNode, ComponentInstance } from '@vue/core'
+import { createRenderer, VNode, Component } from '@vue/core'
 import { nodeOps } from './nodeOps'
 import { patchData } from './patchData'
 import { teardownVNode } from './teardownVNode'
@@ -12,7 +12,7 @@ const { render: _render } = createRenderer({
 type publicRender = (
   node: VNode | null,
   container: HTMLElement
-) => ComponentInstance | null
+) => Component | null
 export const render = _render as publicRender
 
 // re-export everything from core

packages/renderer-dom/src/modules/style.ts

@@ -1,3 +1,5 @@
+import { isString } from '@vue/shared'
+
 // style properties that should NOT have "px" added when numeric
 const nonNumericRE = /acit|ex(?:s|g|n|p|$)|rph|ows|mnc|ntw|ine[ch]|zoo|^ord/i
 
@@ -5,7 +7,7 @@ export function patchStyle(el: any, prev: any, next: any, data: any) {
   const { style } = el
   if (!next) {
     el.removeAttribute('style')
-  } else if (typeof next === 'string') {
+  } else if (isString(next)) {
     style.cssText = next
   } else {
     for (const key in next) {
@@ -15,7 +17,7 @@ export function patchStyle(el: any, prev: any, next: any, data: any) {
       }
       style[key] = value
     }
-    if (prev && typeof prev !== 'string') {
+    if (prev && !isString(prev)) {
       for (const key in prev) {
         if (!next[key]) {
           style[key] = ''