feat(config): expose config.useEventDelegation and default to false

6 years ago · 3be1c5d67e
5 changed files with 24 additions and 2 deletions
--- a/src/core/config.js
+++ b/src/core/config.js
@ -19,6 +19,7 @@ export type Config = {
  warnHandler: ?(msg: string, vm: Component, trace: string) => void;
  ignoredElements: Array<string | RegExp>;
  keyCodes: { [key: string]: number | Array<number> };
+  useEventDelegation: boolean;

  // platform
  isReservedTag: (x?: string) => boolean;
@ -83,6 +84,15 @@ export default ({
  // $flow-disable-line
  keyCodes: Object.create(null),

+  /**
+   * Use event delegation - this works around a few async edge cases caused by
+   * microtask / DOM event racing conditions, and should in theory save some
+   * memory.
+   *
+   * Off by default for backwards compatibility.
+   */
+  useEventDelegation: false,
+
  /**
   * Check if a tag is reserved so that it cannot be registered as a
   * component. This is platform-dependent and may be overwritten.
--- a/src/platforms/web/runtime/modules/events.js
+++ b/src/platforms/web/runtime/modules/events.js
@ -1,5 +1,6 @@
 /* @flow */

+import config from 'core/config'
 import { isDef, isUndef } from 'shared/util'
 import { updateListeners } from 'core/vdom/helpers/index'
 import { isIE, isPhantomJS, supportsPassive } from 'core/util/index'
@ -50,7 +51,12 @@ function add (
  capture: boolean,
  passive: boolean
 ) {
-  if (!capture && !passive && delegateRE.test(name)) {
+  if (
+    !capture &&
+    !passive &&
+    config.useEventDelegation &&
+    delegateRE.test(name)
+  ) {
    const count = eventCounts[name]
    let store = target.__events
    if (!count) {
@ -150,7 +156,7 @@ function remove (
  _target?: HTMLElement
 ) {
  const el: any = _target || target
-  if (!capture && delegateRE.test(name)) {
+  if (!capture && config.useEventDelegation && delegateRE.test(name)) {
    el.__events[name] = null
    if (--eventCounts[name] === 0) {
      removeGlobalHandler(name)
--- a/test/e2e/specs/async-edge-cases.html
+++ b/test/e2e/specs/async-edge-cases.html
@ -6,6 +6,10 @@
    <script src="../../../dist/vue.min.js"></script>
  </head>
  <body>
+    <script>
+      // this is necessary to make these cases pass
+      Vue.config.useEventDelegation = true
+    </script>

    <!-- #4510 click and change event on checkbox -->
    <div id="case-1">
--- a/types/test/vue-test.ts
+++ b/types/test/vue-test.ts
@ -75,6 +75,7 @@ class Test extends Vue {
    config.keyCodes = { esc: 27 };
    config.ignoredElements = ['foo', /^ion-/];
    config.async = false
+    config.useEventDelegation = true
  }

  static testMethods() {
--- a/types/vue.d.ts
+++ b/types/vue.d.ts
@ -74,6 +74,7 @@ export interface VueConfiguration {
  warnHandler(msg: string, vm: Vue, trace: string): void;
  ignoredElements: (string | RegExp)[];
  keyCodes: { [key: string]: number | number[] };
+  useEventDelegation: boolean;
  async: boolean;
 }