Event.eventPhase - Web APIs 编辑
The eventPhase
read-only property of the Event
interface indicates which phase of the event flow is currently being evaluated.
Syntax
let phase = event.eventPhase;
Value
Returns an integer value which specifies the current evaluation phase of the event flow. Possible values are listed in Event phase constants.
Constants
Event phase constants
These values describe which phase the event flow is currently being evaluated.
Constant | Value | Description |
---|---|---|
Event.NONE | 0 | No event is being processed at this time. |
Event.CAPTURING_PHASE | 1 | The event is being propagated through the target's ancestor objects. This process starts with the Window , then Document , then the HTMLHtmlElement , and so on through the elements until the target's parent is reached. Event listeners registered for capture mode when EventTarget.addEventListener() was called are triggered during this phase. |
Event.AT_TARGET | 2 | The event has arrived at the event's target. Event listeners registered for this phase are called at this time. If Event.bubbles is false , processing the event is finished after this phase is complete. |
Event.BUBBLING_PHASE | 3 | The event is propagating back up through the target's ancestors in reverse order, starting with the parent, and eventually reaching the containing Window . This is known as bubbling, and occurs only if Event.bubbles is true . Event listeners registered for this phase are triggered during this process. |
For more details, see section 3.1, Event dispatch and DOM event flow, of the DOM Level 3 Events specification.
Example
HTML
<h4>Event Propagation Chain</h4>
<ul>
<li>Click 'd1'</li>
<li>Analyse event propagation chain</li>
<li>Click next div and repeat the experience</li>
<li>Change Capturing mode</li>
<li>Repeat the experience</li>
</ul>
<input type="checkbox" id="chCapture" />
<label for="chCapture">Use Capturing</label>
<div id="d1">d1
<div id="d2">d2
<div id="d3">d3
<div id="d4">d4</div>
</div>
</div>
</div>
<div id="divInfo"></div>
CSS
div {
margin: 20px;
padding: 4px;
border: thin black solid;
}
#divInfo {
margin: 18px;
padding: 8px;
background-color:white;
font-size:80%;
}
JavaScript
let clear = false,
divInfo = null,
divs = null,
useCapture = false;
window.onload = function () {
divInfo = document.getElementById('divInfo')
divs = document.getElementsByTagName('div')
chCapture = document.getElementById('chCapture')
chCapture.onclick = function () {
RemoveListeners()
AddListeners()
}
Clear()
AddListeners()
}
function RemoveListeners() {
for (let i = 0; i < divs.length; i++) {
let d = divs[i]
if (d.id != "divInfo") {
d.removeEventListener("click", OnDivClick, true)
d.removeEventListener("click", OnDivClick, false)
}
}
}
function AddListeners() {
for (let i = 0; i < divs.length; i++) {
let d = divs[i]
if (d.id != "divInfo") {
if (chCapture.checked) {
d.addEventListener("click", OnDivClick, true)
}
else {
d.addEventListener("click", OnDivClick, false)
d.onmousemove = function () { clear = true }
}
}
}
}
function OnDivClick(e) {
if (clear) {
Clear()
clear = false
}
if (e.eventPhase == 2)
e.currentTarget.style.backgroundColor = 'red';
const level =
e.eventPhase == 0 ? "none" :
e.eventPhase == 1 ? "capturing" :
e.eventPhase == 2 ? "target" :
e.eventPhase == 3 ? "bubbling" : "error";
const p = document.createElement('p')
p.textContent = `${e.currentTarget.id}; eventPhase: ${level}`;
divInfo.appendChild(p);
}
function Clear() {
for (let i = 0; i < divs.length; i++) {
if (divs[i].id != "divInfo") {
divs[i].style.backgroundColor = (i & 1) ? "#f6eedb" : "#cceeff"
}
}
divInfo.textContent = '';
}
Result
Specifications
Specification | Status | Comment |
---|---|---|
DOM The definition of 'Event.eventPhase' in that specification. | Living Standard | |
DOM4 The definition of 'Event.eventPhase' in that specification. | Obsolete | |
Document Object Model (DOM) Level 2 Events Specification The definition of 'Event.eventPhase' in that specification. | Obsolete | Initial definition |
Browser compatibility
BCD tables only load in the browser
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