<!DOCTYPE html>
<head>
<style>
#box {
width: 200px;
height: 200px;
background-color: lightblue;
}
</style>
</head>
<body>
<div id="box"></div>
</body>
<script src="../include.js"></script>
<script>
asyncTest(async done => {
const box = document.getElementById("box");
let resolve = null;
function createResizeObserverPromise() {
return new Promise(r => {
resolve = r;
});
}
function createTimeoutPromise(timeout) {
return new Promise(r => {
setTimeout(r, timeout);
});
}
const resizeObserver = new ResizeObserver(entries => {
for (let entry of entries) {
const { width, height } = entry.contentRect;
println(`Size changed: ${width}px x ${height}px`);
}
if (resolve) resolve();
});
let observerCallbackInvocation = createResizeObserverPromise();
resizeObserver.observe(box);
await observerCallbackInvocation;
resizeObserver.unobserve(box);
box.style.width = "400px";
box.style.height = "400px";
// Let event loop run to ensure that observer callback is not invoked.
await createTimeoutPromise(0);
done();
});
</script>
