HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>bubbles parent</title>
  <style>
    #parent { padding: 16px; border: 2px solid #2563eb; background: #eff6ff; }
    #child { padding: 12px; border: 2px dashed #7c3aed; background: #f5f3ff; }
  </style>
</head>
<body>
  <div id="parent">
    Parent
    <div id="child">Child</div>
  </div>
  <button id="fire" type="button">Dispatch bubbling ping</button>
  <button id="fireLocal" type="button">Dispatch non-bubbling ping</button>
  <pre id="out">Waiting...</pre>
  <script>
    var parent = document.getElementById("parent");
    var child = document.getElementById("child");
    var out = document.getElementById("out");

    parent.addEventListener("ping", function () {
      out.textContent = "parent heard ping (bubbled)";
    });

    document.getElementById("fire").onclick = function () {
      out.textContent = "...";
      child.dispatchEvent(new Event("ping", { bubbles: true }));
      if (out.textContent === "...") out.textContent = "parent did not hear it";
    };

    document.getElementById("fireLocal").onclick = function () {
      out.textContent = "...";
      child.dispatchEvent(new Event("ping", { bubbles: false }));
      if (out.textContent === "...") out.textContent = "parent did not hear it (bubbles=false)";
    };
  </script>
</body>
</html>

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Event.bubbles — parent hears child (Try It)