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
183
184
185
186
187
188
189
190
|
---
title: resize
slug: Web/API/Window/resize_event
translation_of: Web/API/Window/resize_event
---
<p><span class="seoSummary">O evento <strong><code>resize</code></strong> é disparado quando o document view é redimensionado.</span></p>
<p>O evento manipulador pode ser registrado para o evento <code>resize</code> usando o atributo <code>window.onresize</code> ou usando <code>window.addEventListener('resize', ...)</code> </p>
<p>Em alguns browsers mais recentes é possível registrar o evento manipulador <code>resize</code> em qualquer elemento HTML. E ainda é possível adicionar atributos <code>onresize</code> ou usar {{domxref("EventTarget.addEventListener", "addEventListener()")}} para implementar o manipulador em qualquer elemento. Entretanto, eventos <code>resize</code> apenas são disparados sobre (enviados para) o objeto {{domxref("Window", "window")}} ({{domxref("document.defaultView")}}). Apenas manipuladores registrados no objeto <code>window</code> recebem os eventos.</p>
<p>Existe uma nova proposta (2017) para permitir que todos os elementos sejam notificados de alterações de tamanho. Veja <a href="https://wicg.github.io/ResizeObserver/">Resize Observer</a> para ler o documento rascunho, e <a href="https://github.com/WICG/ResizeObserver/issues">Github issues</a> para ler as discussões do que está ativo.</p>
<h2 id="Informações_gerais">Informações gerais</h2>
<dl>
<dt style="float: left; text-align: right; width: 120px;">Specifications</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;">Interface</dt>
<dd style="margin: 0 0 0 120px;">UIEvent</dd>
<dt style="float: left; text-align: right; width: 120px;">Bubbles</dt>
<dd style="margin: 0 0 0 120px;">Não</dd>
<dt style="float: left; text-align: right; width: 120px;">Cancelable</dt>
<dd style="margin: 0 0 0 120px;">Não</dd>
<dt style="float: left; text-align: right; width: 120px;">Target</dt>
<dd style="margin: 0 0 0 120px;">defaultView (window)</dd>
<dt style="float: left; text-align: right; width: 120px;">Default Action</dt>
<dd style="margin: 0 0 0 120px;">Nenhuma</dd>
</dl>
<h2 id="Properties">Properties</h2>
<table class="standard-table">
<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>O evento alto (o primeiro alvo na árvore DOM).</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>O tipo de evento.</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>Se o evento normalmente bubbles ou não.</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>Se o evento é cancelado ou não.</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> do documento)</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="Examples">Examples</h2>
<p>Como os eventos <code>resize</code> podem ser altamente executados, o evento manipulador não deve executar operações computacionais caras como modificações DOM. Em vez disso, recomenda-se diminuir o impacto do evento usando <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> ou <a href="/en-US/docs/Web/API/CustomEvent">customEvent</a>*, como a seguir:<br>
<br>
<strong>* IMPORTANT: </strong>Por favor note que IE11 precisa do <a href="https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill">customEvent</a> polyfill para funcionar corretamente.</p>
<h3 id="requestAnimationFrame_customEvent">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">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">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>
|
