1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
---
title: resize
slug: Web/API/Window/resize_event
translation_of: Web/API/Window/resize_event
---
<p style="font-family: Microsoft Yahei;"><span class="seoSummary">文档视图调整大小时会触发 <strong>resize</strong> 事件。</span></p>
<h2 id="基本信息" style="font-family: Microsoft Yahei;">基本信息</h2>
<dl style="font-family: Microsoft Yahei;">
<dt style="float: left; text-align: right; width: 120px;">规范</dt>
<dd style="margin: 0 0 0 120px;"><a class="external" href="http://www.w3.org/TR/DOM-Level-3-Events/#event-type-resize">DOM L3</a>, <a href="http://www.w3.org/TR/cssom-view/#resizing-viewports">CSSOM View</a></dd>
<dt style="float: left; text-align: right; width: 120px;">接口</dt>
<dd style="margin: 0 0 0 120px;">UIEvent</dd>
<dt style="float: left; text-align: right; width: 120px;">是否冒泡</dt>
<dd style="margin: 0 0 0 120px;">否</dd>
<dt style="float: left; text-align: right; width: 120px;">是否可取消默认</dt>
<dd style="margin: 0 0 0 120px;">否</dd>
<dt style="float: left; text-align: right; width: 120px;">事件目标</dt>
<dd style="margin: 0 0 0 120px;">defaultView (window)</dd>
<dt style="float: left; text-align: right; width: 120px;">默认行为</dt>
<dd style="margin: 0 0 0 120px;">None</dd>
</dl>
<h2 id="属性" style="font-family: Microsoft Yahei;">属性</h2>
<table class="standard-table" style="font-family: Microsoft Yahei;">
<thead>
<tr>
<th scope="col">Property</th>
<th scope="col">Type</th>
<th scope="col">Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>target</code> {{readonlyInline}}</td>
<td><a href="/en-US/docs/Web/API/EventTarget" title="EventTarget is an interface implemented by objects that can receive events and may have listeners for them."><code>EventTarget</code></a></td>
<td>The event target (the topmost target in the DOM tree).</td>
</tr>
<tr>
<td><code>type</code> {{readonlyInline}}</td>
<td><a href="/en-US/docs/Web/API/DOMString" title="DOMString is a UTF-16 String. As JavaScript already uses such strings, DOMString is mapped directly to a String."><code>DOMString</code></a></td>
<td>The type of event.</td>
</tr>
<tr>
<td><code>bubbles</code> {{readonlyInline}}</td>
<td><a href="/en-US/docs/Web/API/Boolean" title="The Boolean object is an object wrapper for a boolean value."><code>Boolean</code></a></td>
<td>Whether the event normally bubbles or not.</td>
</tr>
<tr>
<td><code>cancelable</code> {{readonlyInline}}</td>
<td><a href="/en-US/docs/Web/API/Boolean" title="The Boolean object is an object wrapper for a boolean value."><code>Boolean</code></a></td>
<td>Whether the event is cancellable or not.</td>
</tr>
<tr>
<td><code>view</code> {{readonlyInline}}</td>
<td><a class="new" href="/en-US/docs/Web/API/WindowProxy" rel="nofollow" title="The documentation about this has not yet been written; please consider contributing!"><code>WindowProxy</code></a></td>
<td><a href="/en-US/docs/Web/API/Document/defaultView" title="In browsers, document.defaultView returns the window object associated with a document, or null if none is available."><code>document.defaultView</code></a> (<code>window</code> of the document)</td>
</tr>
<tr>
<td><code>detail</code> {{readonlyInline}}</td>
<td><code>long</code> (<code>float</code>)</td>
<td>0.</td>
</tr>
</tbody>
</table>
<h2 id="案例" style="font-family: Microsoft Yahei;">案例</h2>
<p style="font-family: Microsoft Yahei;">由于resize事件可以以较高的速率触发, 因此事件处理程序不应该执行计算开销很大的操作 (如 DOM 修改)。相反, 建议使用<a href="/en-US/docs/DOM/window.requestAnimationFrame" title="/en-US/docs/DOM/window.requestAnimationFrame">requestAnimationFrame</a>, <a href="/en-US/docs/Web/API/WindowTimers/setTimeout">setTimeout</a> or <a href="/en-US/docs/Web/API/CustomEvent">customEvent</a>, 比如:</p>
<h3 id="requestAnimationFrame_customEvent" style="font-family: Microsoft Yahei;">requestAnimationFrame + customEvent</h3>
<pre class="brush: js">;(function() {
var throttle = function(type, name, obj) {
obj = obj || window;
var running = false;
var func = function() {
if (running) { return; }
running = true;
requestAnimationFrame(function() {
obj.dispatchEvent(new CustomEvent(name));
running = false;
});
};
obj.addEventListener(type, func);
};
/* init - you can init any event */
throttle("resize", "optimizedResize");
})();
// handle event
window.addEventListener("optimizedResize", function() {
console.log("Resource conscious resize callback!");
});
</pre>
<h3 id="requestAnimationFrame" style="font-family: Microsoft Yahei;">requestAnimationFrame</h3>
<pre class="brush: js">var optimizedResize = (function() {
var callbacks = [],
running = false;
// fired on resize event
function resize() {
if (!running) {
running = true;
if (window.requestAnimationFrame) {
window.requestAnimationFrame(runCallbacks);
} else {
setTimeout(runCallbacks, 66);
}
}
}
// run the actual callbacks
function runCallbacks() {
callbacks.forEach(function(callback) {
callback();
});
running = false;
}
// adds callback to loop
function addCallback(callback) {
if (callback) {
callbacks.push(callback);
}
}
return {
// public method to add additional callback
add: function(callback) {
if (!callbacks.length) {
window.addEventListener('resize', resize);
}
addCallback(callback);
}
}
}());
// start process
optimizedResize.add(function() {
console.log('Resource conscious resize callback!')
});
</pre>
<h3 id="setTimeout" style="font-family: Microsoft Yahei;">setTimeout</h3>
<pre class="brush: js">(function() {
window.addEventListener("resize", resizeThrottler, false);
var resizeTimeout;
function resizeThrottler() {
// ignore resize events as long as an actualResizeHandler execution is in the queue
if ( !resizeTimeout ) {
resizeTimeout = setTimeout(function() {
resizeTimeout = null;
actualResizeHandler();
// The actualResizeHandler will execute at a rate of 15fps
}, 66);
}
}
function actualResizeHandler() {
// handle the resize event
...
}
}());</pre>
|
