lib/goog/events/event.js

1// Copyright 2005 The Closure Library Authors. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS-IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15/**
16 * @fileoverview A base class for event objects.
17 *
18 */
19
20
21goog.provide('goog.events.Event');
22goog.provide('goog.events.EventLike');
23
24/**
25 * goog.events.Event no longer depends on goog.Disposable. Keep requiring
26 * goog.Disposable here to not break projects which assume this dependency.
27 * @suppress {extraRequire}
28 */
29goog.require('goog.Disposable');
30goog.require('goog.events.EventId');
31
32
33/**
34 * A typedef for event like objects that are dispatchable via the
35 * goog.events.dispatchEvent function. strings are treated as the type for a
36 * goog.events.Event. Objects are treated as an extension of a new
37 * goog.events.Event with the type property of the object being used as the type
38 * of the Event.
39 * @typedef {string|Object|goog.events.Event|goog.events.EventId}
40 */
41goog.events.EventLike;
42
43
44
45/**
46 * A base class for event objects, so that they can support preventDefault and
47 * stopPropagation.
48 *
49 * @param {string|!goog.events.EventId} type Event Type.
50 * @param {Object=} opt_target Reference to the object that is the target of
51 * this event. It has to implement the {@code EventTarget} interface
52 * declared at {@link http://developer.mozilla.org/en/DOM/EventTarget}.
53 * @constructor
54 */
55goog.events.Event = function(type, opt_target) {
56 /**
57 * Event type.
58 * @type {string}
59 */
60 this.type = type instanceof goog.events.EventId ? String(type) : type;
61
62 /**
63 * TODO(tbreisacher): The type should probably be
64 * EventTarget|goog.events.EventTarget.
65 *
66 * Target of the event.
67 * @type {Object|undefined}
68 */
69 this.target = opt_target;
70
71 /**
72 * Object that had the listener attached.
73 * @type {Object|undefined}
74 */
75 this.currentTarget = this.target;
76
77 /**
78 * Whether to cancel the event in internal capture/bubble processing for IE.
79 * @type {boolean}
80 * @public
81 * @suppress {underscore|visibility} Technically public, but referencing this
82 * outside this package is strongly discouraged.
83 */
84 this.propagationStopped_ = false;
85
86 /**
87 * Whether the default action has been prevented.
88 * This is a property to match the W3C specification at
89 * {@link http://www.w3.org/TR/DOM-Level-3-Events/
90 * #events-event-type-defaultPrevented}.
91 * Must be treated as read-only outside the class.
92 * @type {boolean}
93 */
94 this.defaultPrevented = false;
95
96 /**
97 * Return value for in internal capture/bubble processing for IE.
98 * @type {boolean}
99 * @public
100 * @suppress {underscore|visibility} Technically public, but referencing this
101 * outside this package is strongly discouraged.
102 */
103 this.returnValue_ = true;
104};
105
106
107/**
108 * For backwards compatibility (goog.events.Event used to inherit
109 * goog.Disposable).
110 * @deprecated Events don't need to be disposed.
111 */
112goog.events.Event.prototype.disposeInternal = function() {
113};
114
115
116/**
117 * For backwards compatibility (goog.events.Event used to inherit
118 * goog.Disposable).
119 * @deprecated Events don't need to be disposed.
120 */
121goog.events.Event.prototype.dispose = function() {
122};
123
124
125/**
126 * Stops event propagation.
127 */
128goog.events.Event.prototype.stopPropagation = function() {
129 this.propagationStopped_ = true;
130};
131
132
133/**
134 * Prevents the default action, for example a link redirecting to a url.
135 */
136goog.events.Event.prototype.preventDefault = function() {
137 this.defaultPrevented = true;
138 this.returnValue_ = false;
139};
140
141
142/**
143 * Stops the propagation of the event. It is equivalent to
144 * {@code e.stopPropagation()}, but can be used as the callback argument of
145 * {@link goog.events.listen} without declaring another function.
146 * @param {!goog.events.Event} e An event.
147 */
148goog.events.Event.stopPropagation = function(e) {
149 e.stopPropagation();
150};
151
152
153/**
154 * Prevents the default action. It is equivalent to
155 * {@code e.preventDefault()}, but can be used as the callback argument of
156 * {@link goog.events.listen} without declaring another function.
157 * @param {!goog.events.Event} e An event.
158 */
159goog.events.Event.preventDefault = function(e) {
160 e.preventDefault();
161};