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Test Info:
- This WPT test may be referenced by the following Test IDs:
- /css/cssom/MutationObserver-style.html - WPT Dashboard Interop Dashboard
<!doctype html>
<meta charset=utf-8>
<title>Observer notifications when updating styles</title>
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<body>
<script>
"use strict";
promise_test(async () => {
let called = 0;
const el = document.createElement("div");
document.body.appendChild(el);
const m = new MutationObserver(() => {
called++;
});
m.observe(el, { attributes: true });
el.style.height = "100px";
await Promise.resolve();
assert_equals(called, 1, "times callback called");
el.style.height = "100px";
await Promise.resolve();
assert_equals(called, 1, "times callback called");
}, "Updating style property with the same value does not trigger an observation callback");
promise_test(async () => {
let called = 0;
const el = document.createElement("div");
document.body.appendChild(el);
const m = new MutationObserver(() => {
called++;
});
m.observe(el, { attributes: true });
el.style.cssText = "height:100px";
await Promise.resolve();
assert_equals(called, 1, "times callback called");
el.style.cssText = "height:100px";
await Promise.resolve();
assert_equals(called, 2, "times callback called");
}, "Updating cssText triggers an observation callback even if the value is the same");
</script>