Source code

Revision control

Copy as Markdown

Other Tools

Test Info: Warnings

<!DOCTYPE html>
<meta name="viewport" content="width=device-width,initial-scale=1">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="./resources/intersection-observer-test-utils.js"></script>
<style>
#scroller { width: 100px; height: 100px; overflow: scroll; }
#scroller > div { height: 800px; }
#target { margin-top: 25px; height: 50px; background-color: blue; }
</style>
<div id="scroller">
<div>
<div id="target"></div>
</div>
</div>
<script>
let entries = [];
window.onload = function() {
runTestCycle(step2, "At initial scroll position");
scroller.scrollTop = 0;
let observer = new IntersectionObserver(
es => entries = entries.concat(es),
{ threshold: 1 }
);
observer.observe(target);
};
function step2() {
runTestCycle(step3, "Scrolled to half way through target element");
assert_equals(entries.length, 1);
assert_equals(entries[0].intersectionRatio, 1);
assert_equals(entries[0].isIntersecting, true);
scroller.scrollTop = 50;
}
function step3() {
runTestCycle(step4, "Scrolled to target element completely off screen");
assert_equals(entries.length, 2);
assert_true(entries[1].intersectionRatio >= 0.5 &&
entries[1].intersectionRatio < 1);
assert_equals(entries[1].isIntersecting, false);
scroller.scrollTop = 100;
}
function step4() {
assert_equals(entries.length, 2);
}
</script>