From c660917b29ed8c1994b497937ea67c80b56a8be2 Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Fri, 13 Jan 2017 19:44:32 -0500
Subject: [PATCH] improve event update algorithm (thanks to suggestions from
 @defcc)

---
 src/core/vdom/helpers/update-listeners.js     | 96 +++++++++----------
 test/unit/modules/vdom/modules/events.spec.js | 12 ++-
 2 files changed, 56 insertions(+), 52 deletions(-)

diff --git a/src/core/vdom/helpers/update-listeners.js b/src/core/vdom/helpers/update-listeners.js
index 674a7cab..2af4a0c7 100644
--- a/src/core/vdom/helpers/update-listeners.js
+++ b/src/core/vdom/helpers/update-listeners.js
@@ -1,7 +1,44 @@
 /* @flow */
 
+import { cached } from 'shared/util'
 import { warn } from 'core/util/index'
 
+const normalizeEvent = cached((name: string): {
+  name: string,
+  once: boolean,
+  capture: boolean
+} => {
+  const once = name.charAt(0) === '~' // Prefixed last, checked first
+  name = once ? name.slice(1) : name
+  const capture = name.charAt(0) === '!'
+  name = capture ? name.slice(1) : name
+  return {
+    name,
+    once,
+    capture
+  }
+})
+
+function createEventHandle (fn: Function | Array<Function>): {
+  fn: Function | Array<Function>;
+  invoker: Function;
+} {
+  const handle = {
+    fn,
+    invoker: function () {
+      const fn = handle.fn
+      if (Array.isArray(fn)) {
+        for (let i = 0; i < fn.length; i++) {
+          fn[i].apply(null, arguments)
+        }
+      } else {
+        fn.apply(null, arguments)
+      }
+    }
+  }
+  return handle
+}
+
 export function updateListeners (
   on: Object,
   oldOn: Object,
@@ -9,69 +46,30 @@ export function updateListeners (
   remove: Function,
   vm: Component
 ) {
-  let name, cur, old, curIsArray, oldIsArray, fn, event, capture, once
+  let name, cur, old, event
   for (name in on) {
     cur = on[name]
     old = oldOn[name]
-    curIsArray = Array.isArray(cur)
-    oldIsArray = Array.isArray(old)
+    event = normalizeEvent(name)
     if (!cur) {
       process.env.NODE_ENV !== 'production' && warn(
-        `Invalid handler for event "${name}": got ` + String(cur),
+        `Invalid handler for event "${event.name}": got ` + String(cur),
         vm
       )
     } else if (!old) {
-      once = name.charAt(0) === '~' // Prefixed last, checked first
-      event = once ? name.slice(1) : name
-      capture = event.charAt(0) === '!'
-      event = capture ? event.slice(1) : event
-      if (curIsArray) {
-        add(event, (cur.invoker = arrInvoker(cur)), once, capture)
-      } else {
-        if (!cur.invoker) {
-          fn = cur
-          cur = on[name] = {}
-          cur.fn = fn
-          cur.invoker = fnInvoker(cur)
-        }
-        add(event, cur.invoker, once, capture)
+      if (!cur.invoker) {
+        cur = on[name] = createEventHandle(cur)
       }
+      add(event.name, cur.invoker, event.once, event.capture)
     } else if (cur !== old) {
-      if (curIsArray || oldIsArray) {
-        if (!curIsArray) cur = [cur]
-        if (!oldIsArray) old = [old]
-        old.length = cur.length
-        for (let i = 0; i < old.length; i++) old[i] = cur[i]
-        on[name] = old
-      } else {
-        old.fn = cur
-        on[name] = old
-      }
+      old.fn = cur
+      on[name] = old
     }
   }
   for (name in oldOn) {
     if (!on[name]) {
-      once = name.charAt(0) === '~' // Prefixed last, checked first
-      event = once ? name.slice(1) : name
-      capture = event.charAt(0) === '!'
-      event = capture ? event.slice(1) : event
-      remove(event, oldOn[name].invoker, capture)
-    }
-  }
-}
-
-function arrInvoker (arr: Array<Function>): Function {
-  return function (ev) {
-    const single = arguments.length === 1
-    for (let i = 0; i < arr.length; i++) {
-      single ? arr[i](ev) : arr[i].apply(null, arguments)
+      event = normalizeEvent(name)
+      remove(event.name, oldOn[name].invoker, event.capture)
     }
   }
 }
-
-function fnInvoker (o: { fn: Function }): Function {
-  return function (ev) {
-    const single = arguments.length === 1
-    single ? o.fn(ev) : o.fn.apply(null, arguments)
-  }
-}
diff --git a/test/unit/modules/vdom/modules/events.spec.js b/test/unit/modules/vdom/modules/events.spec.js
index 1da758f1..9dcd72c4 100644
--- a/test/unit/modules/vdom/modules/events.spec.js
+++ b/test/unit/modules/vdom/modules/events.spec.js
@@ -105,24 +105,30 @@ describe('vdom events module', () => {
     const click = jasmine.createSpy()
     const click2 = jasmine.createSpy()
     const click3 = jasmine.createSpy()
+    const vnode0 = new VNode('a', { on: { click: click }})
     const vnode1 = new VNode('a', { on: { click: [click, click2] }})
     const vnode2 = new VNode('a', { on: { click: click }})
     const vnode3 = new VNode('a', { on: { click: [click2, click3] }})
 
-    const elm = patch(null, vnode1)
+    const elm = patch(null, vnode0)
     document.body.appendChild(elm)
     triggerEvent(elm, 'click')
     expect(click.calls.count()).toBe(1)
+    expect(click2.calls.count()).toBe(0)
+
+    patch(vnode0, vnode1)
+    triggerEvent(elm, 'click')
+    expect(click.calls.count()).toBe(2)
     expect(click2.calls.count()).toBe(1)
 
     patch(vnode1, vnode2)
     triggerEvent(elm, 'click')
-    expect(click.calls.count()).toBe(2)
+    expect(click.calls.count()).toBe(3)
     expect(click2.calls.count()).toBe(1)
 
     patch(vnode2, vnode3)
     triggerEvent(elm, 'click')
-    expect(click.calls.count()).toBe(2)
+    expect(click.calls.count()).toBe(3)
     expect(click2.calls.count()).toBe(2)
     expect(click3.calls.count()).toBe(1)
   })