Event: eventPhase property

The eventPhase read-only property of the {{domxref("Event")}} interface indicates which phase of the event flow is currently being evaluated.

Value

Returns an integer value which specifies the current evaluation phase of the event flow. Possible values are:

Event.NONE (0)
- : The event is not 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 {{domxref("Window")}}, then {{domxref("Document")}}, then the {{domxref("HTMLHtmlElement")}}, and so on through the elements until the target's parent is reached. {{domxref("EventTarget/addEventListener", "Event listeners", "", 1)}} registered for capture mode when {{domxref("EventTarget.addEventListener()")}} was called are triggered during this phase.
Event.AT_TARGET (2)
- : The event has arrived at {{domxref("EventTarget", "the event's target", "", 1)}}. Event listeners registered for this phase are called at this time. If {{domxref("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 {{domxref("Window")}}. This is known as bubbling, and occurs only if {{domxref("Event.bubbles")}} is true. {{domxref("EventTarget/addEventListener", "Event listeners", "", 1)}} registered for this phase are triggered during this process.

Example

HTML

html

<h4>Event Propagation Chain</h4>
<ul>
  <li>Click 'd1'</li>
  <li>Analyze 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

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;
const divInfo = document.getElementById("divInfo");
const divs = document.getElementsByTagName("div");
const chCapture = document.getElementById("chCapture");

chCapture.addEventListener("click", () => {
  removeListeners();
  addListeners();
  clearDivs();
});
clearDivs();
addListeners();

function removeListeners() {
  for (const div of divs) {
    if (div.id !== "divInfo") {
      div.removeEventListener("click", onDivClick, true);
      div.removeEventListener("click", onDivClick, false);
    }
  }
}

function addListeners() {
  for (const div of divs) {
    if (div.id !== "divInfo") {
      if (chCapture.checked) {
        div.addEventListener("click", onDivClick, true);
      } else {
        div.addEventListener("click", onDivClick, false);
        div.onmousemove = () => {
          clear = true;
        };
      }
    }
  }
}

function onDivClick(e) {
  if (clear) {
    clearDivs();
    clear = false;
  }
  if (e.eventPhase === 2) {
    e.currentTarget.style.backgroundColor = "red";
  }
  const level =
    ["none", "capturing", "target", "bubbling"][e.eventPhase] ?? "error";
  const para = document.createElement("p");
  para.textContent = `${e.currentTarget.id}; eventPhase: ${level}`;
  divInfo.appendChild(para);
}

function clearDivs() {
  for (let i = 0; i < divs.length; i++) {
    if (divs[i].id !== "divInfo") {
      divs[i].style.backgroundColor = i % 2 !== 0 ? "#f6eedb" : "#cceeff";
    }
  }
  divInfo.textContent = "";
}

Value

Example

HTML

CSS

JavaScript

Result

Specifications

Browser compatibility