Event.eventPhase

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表示事件物件目前於事件流(Event Flow)中傳遞的進度為哪一個階段。

語法

var phase = event.eventPhase;

回傳一個整數值以代表目前事件於事件流中的傳遞階段,可能的值將於事件傳遞階段常數說明。

常數

事件傳遞階段常數

These values describe which phase the event flow is currently being evaluated.

常數 說明
Event.NONE Read only 0 No event is being processed at this time.
Event.CAPTURING_PHASE Read only 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 Read only 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 Read only 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.

範例

HTML Content

<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 Content

div { 
  margin: 20px;
  padding: 4px;
  border: thin black solid;
} 

#divInfo { 
  margin: 18px;
  padding: 8px;
  background-color:white;
  font-size:80%; 
}

JavaScript Content

var 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 (var i = 0; i < divs.length; i++) { 
    var d = divs[i]; 
    if (d.id != "divInfo") { 
      d.removeEventListener("click", OnDivClick, true);
      d.removeEventListener("click", OnDivClick, false);
    }
  }
}

function AddListeners() { 
  for (var i = 0; i < divs.length; i++) { 
    var d = divs[i];
    if (d.id != "divInfo") { 
      d.addEventListener("click", OnDivClick, false); 
      if (chCapture.checked) 
        d.addEventListener("click", OnDivClick, true);
      d.onmousemove = function () { clear = true; }; 
    }
  }
} 

function OnDivClick(e) {
  if (clear) {
    Clear(); clear = false;
  }
  if (e.eventPhase == 2)
    e.currentTarget.style.backgroundColor = 'red';
  var level = e.eventPhase == 0 ? "none" : e.eventPhase == 1 ? "capturing" : e.eventPhase == 2 ? "target" : e.eventPhase == 3 ? "bubbling" : "error";
  divInfo.innerHTML += e.currentTarget.id + "; eventPhase: " + level + "<br/>";
}

function Clear() { 
  for (var i = 0; i < divs.length; i++) { 
    if (divs[i].id != "divInfo")
      divs[i].style.backgroundColor = (i & 1) ? "#f6eedb" : "#cceeff";
  } 
  divInfo.innerHTML = ''; 
}

規範

Specification Status Comment
DOM
The definition of 'Event.eventPhase' in that specification.
Living Standard  
DOM4
The definition of 'Event.eventPhase' in that specification.
Recommendation  
Document Object Model (DOM) Level 2 Events Specification
The definition of 'Event.eventPhase' in that specification.
Recommendation Initial definition

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