只读
composed
特性为
事件
interface returns a
布尔
which indicates whether or not the event will propagate across the shadow DOM boundary into the standard DOM.
注意
: This property was formerly named
scoped
.
const isComposed = Event.composed;
A
布尔
which is
true
if the event will cross from the shadow DOM into the standard DOM after reaching the shadow root. (That is, the first node in the shadow DOM in which the event began to propagate.)
All UA-dispatched UI events are composed (click/touch/mouseover/copy/paste, etc.). Most other types of events are not composed, and so will return
false
. For example, this includes synthetic events that are created without their
composed
option wil set to
true
.
Propagation only occurs if the
bubbles
property is also
true
. However, capturing only composed events are also handled at host as if they were in
AT_TARGET
phase. You can determine the path the event will follow through the shadow root to the DOM root by calling
composedPath()
.
If this value is
false
, the shadow root will be the last node to be offered the event.
In our composed-composed-path example (see it live), we define two trivial custom elements,
<open-shadow>
and
<closed-shadow>
, both of which take the contents of their text attribute and insert them into the element's shadow DOM as the text content of a
<p>
element. The only difference between the two is that their shadow roots are attached with their modes set to
open
and
closed
分别。
The first definition looks like this, for example:
customElements.define('open-shadow',
class extends HTMLElement {
constructor() {
super();
let pElem = document.createElement('p');
pElem.textContent = this.getAttribute('text');
let shadowRoot = this.attachShadow({mode: 'open'})
.appendChild(pElem);
}
});
We then insert one of each element into our page:
<open-shadow text="I have an open shadow root"></open-shadow> <closed-shadow text="I have a closed shadow root"></closed-shadow>
Then include a click event listener on the
<html>
元素：
document.querySelector('html').addEventListener('click',function(e) {
console.log(e.composed);
console.log(e.composedPath());
});
When you click on the
<open-shadow>
element and then the
<closed-shadow>
element, you'll notice two things.
composed
property returns
true
beause the
click
event is always able to propagate across shadow boundaries.
composedPath
for the two elements.
<open-shadow>
element's composed path is this:
Array [ p, ShadowRoot, open-shadow, body, html, HTMLDocument https://mdn.github.io/web-components-examples/composed-composed-path/, Window ]
Whereas the
<closed-shadow>
element's composed path is a follows:
Array [ closed-shadow, body, html, HTMLDocument https://mdn.github.io/web-components-examples/composed-composed-path/, Window ]
In the second case, the event listeners only propagate as far as the
<closed-shadow>
element itself, but not to the nodes inside the shadow boundary.
| 规范 | 状态 | 注释 |
|---|---|---|
|
DOM
The definition of 'composed' in that specification. |
实时标准 |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
composed
|
Chrome 53 | Edge 79 | Firefox 52 | IE 不支持 No | Opera 40 | Safari Yes | WebView Android 53 | Chrome Android 53 | Firefox Android 52 | Opera Android 41 | Safari iOS Yes | Samsung Internet Android 6.0 |
完整支持
不支持