Web/API/Event/eventPhase

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

Result

Specifications

Specification	Status	Comment
DOMThe definition of 'Event.eventPhase' in that specification.	Living Standard
DOM4The definition of 'Event.eventPhase' in that specification.	Obsolete
Document Object Model (DOM) Level 2 Events SpecificationThe definition of 'Event.eventPhase' in that specification.	Obsolete	Initial definition

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`eventPhase`	Chrome Full support 45	Edge Full support 12	Firefox Full support Yes	IE Full support 9	Opera Full support 32	Safari Full support Yes	WebView Android Full support 45	Chrome Android Full support 45	Firefox Android Full support Yes	Opera Android Full support 32	Safari iOS Full support Yes	Samsung Internet Android Full support 5.0

Legend

Full support: Full support

Event.eventPhase by Mozilla Contributors is licensed under CC-BY-SA 2.5.