event-handler-handleEvent-ignored.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>"handleEvent" property of EventHandler should be ignored</title>
<link rel="help" href="https://html.spec.whatwg.org/#eventhandler">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="log"></div>
<script>
"use strict";

test(t => {
  const handler = Object.create(null, {
    handleEvent: {
      get: t.unreached_func('"handleEvent" property should not be looked up'),
    },
  });

  const el = document.createElement("div");
  el.onmouseenter = handler;
  el.dispatchEvent(new MouseEvent("mouseenter"));
}, 'plain object "mouseenter" handler');

async_test(t => {
  const handler = Object.create(Function.prototype, {
    handleEvent: {
      get: t.unreached_func('"handleEvent" property should not be looked up'),
    },
  });
  assert_true(handler instanceof Function);

  window.onmessage = handler;
  window.postMessage({}, "*");

  step_timeout(() => {
    t.done();
  }, 50);
}, 'non-callable "message" handler that is instance of Function');
</script>

chromium/third_party/blink/web_tests/external/wpt/html/webappapis/scripting/events/event-handler-handleEvent-ignored.html