refactor(reactivity): define hadKey if necessary (#288)

diff --git a/packages/reactivity/src/baseHandlers.ts b/packages/reactivity/src/baseHandlers.ts
index 005cb3ddb83949b3d8b5e897fdf72d939b3a6f08..0043af73fe5cc759c8d8593cfc5fb05f6b9bfb6e 100644 (file)
--- a/packages/reactivity/src/baseHandlers.ts
+++ b/packages/reactivity/src/baseHandlers.ts
@@ -38,12 +38,12 @@ function set(
   receiver: any
 ): boolean {
   value = toRaw(value)
-  const hadKey = hasOwn(target, key)
   const oldValue = target[key]
   if (isRef(oldValue) && !isRef(value)) {
     oldValue.value = value
     return true
   }
+  const hadKey = hasOwn(target, key)
   const result = Reflect.set(target, key, value, receiver)
   // don't trigger if target is something up in the prototype chain of original
   if (target === toRaw(receiver)) {