let interval: number | null = null; addEventListener("load", () => { if (interval) { throw new Error("Interval is already set"); } interval = setInterval(() => {}, 0); }); addEventListener("unload", () => { if (!interval) { throw new Error("Interval was not set"); } clearInterval(interval); }); Deno.bench("bench", () => { if (!interval) { throw new Error("Interval was not set"); } });