MutationObserver-callback-arguments.html

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This WPT test may be referenced by the following Test IDs:
- /dom/nodes/MutationObserver-callback-arguments.html - WPT Dashboard Interop Dashboard

<!DOCTYPE HTML>

<meta charset=utf-8>

<title>MutationObserver: callback arguments</title>

<link rel="help" href="https://dom.spec.whatwg.org/#notify-mutation-observers">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<div id="mo-target"></div>

<div id="log"></div>

<script>

"use strict";

async_test(t => {

  const moTarget = document.querySelector("#mo-target");

  const mo = new MutationObserver(function(records, observer) {

    t.step(() => {

      assert_equals(this, mo);

      assert_equals(arguments.length, 2);

      assert_true(Array.isArray(records));

      assert_equals(records.length, 1);

      assert_true(records[0] instanceof MutationRecord);

      assert_equals(observer, mo);

      mo.disconnect();

      t.done();

});

});

  mo.observe(moTarget, {attributes: true});

  moTarget.className = "trigger-mutation";

}, "Callback is invoked with |this| value of MutationObserver and two arguments");

</script>