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29 lines
1.3 KiB
HTML
29 lines
1.3 KiB
HTML
<!doctype html>
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<meta charset="utf-8">
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<title>14 wheel scroll</title>
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<link rel="stylesheet" href="../_style.css">
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<script src="../_lib.js"></script>
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<body>
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<main>
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<p>Goal: scroll the box to the bottom. Page rejects raw <code>scrollTop</code> assignment without
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<code>wheel</code> events.</p>
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<div id="box" style="height:200px;overflow:auto;border:1px solid #555;background:#fff;color:#111;padding:8px">
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<div style="height:1200px">scroll me ⬇<br><br>...lots of content...</div>
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</div>
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</main>
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<script>
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Challenge.init({ id: "wheel-scroll", instructions: "scroll the box to its bottom" });
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const box = document.getElementById("box");
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let wheelCount = 0, lastWheelTs = -Infinity;
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box.addEventListener("wheel", (e) => { wheelCount++; lastWheelTs = e.timeStamp; Challenge.log("wheel", { dy: e.deltaY }); }, { passive: true });
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box.addEventListener("scroll", () => {
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Challenge.log("scroll", { top: box.scrollTop });
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if (box.scrollTop + box.clientHeight >= box.scrollHeight - 2) {
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if (wheelCount === 0) Challenge.fail("scrolled to bottom with zero wheel events");
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else if (performance.now() - lastWheelTs > 1500) Challenge.fail("wheel events too far before final scroll");
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else Challenge.pass(`${wheelCount} wheel events accompanied scroll`);
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}
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});
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</script>
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</body>
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