function (...args) {
    // ...
}

// 2022 or later
structuredClone(obj)

Object.keys(obj).length

const params = new URLSearchParams(window.location.search);
if (params.get("whatever") != null) {
    // ...
}

[1, 2, 3, ...theRest]

const today = new Date();
const yesterday = new Date(today);
yesterday.setDate(yesterday.getDate() - 1);

// WARNING: toISOString() converts from local time to UTC
function iso8601(d) {
    const mm = (d.getMonth() + 1 + "").padStart(2, "0");
    const dd = (d.getDate() + "").padStart(2, "0");
    return `${d.getFullYear()}-${mm}-${dd}`;
}