observeDeep receives array of events

src/Util/YEvent.js

@@ -2,26 +2,32 @@
 export default class YEvent {
   constructor (target) {
     this.target = target
+    this._path = null
   }
   get path () {
-    const path = []
-    let type = this.target
-    const y = type._y
-    while (type._parent !== y) {
-      let parent = type._parent
-      if (type._parentSub !== null) {
-        path.push(type._parentSub)
-      } else {
-        // parent is array-ish
-        for (let [i, child] of parent) {
-          if (child === type) {
-            path.push(i)
-            break
+    if (this._path !== null) {
+      return this._path
+    } else {
+      const path = []
+      let type = this.target
+      const y = type._y
+      while (type._parent !== y) {
+        let parent = type._parent
+        if (type._parentSub !== null) {
+          path.push(type._parentSub)
+        } else {
+          // parent is array-ish
+          for (let [i, child] of parent) {
+            if (child === type) {
+              path.push(i)
+              break
+            }
           }
         }
+        type = parent
       }
-      type = parent
+      this._path = path
+      return path
     }
-    return path
   }
 }