humanizeDuration.js

const units = [["ms", 1000], ["s", 60], ["m", 60], ["h", 24], ["d", 7], ["w", 52.142857142858986], ["y", Infinity]];

const duration = (ms) => units.reduce(
    ({ left, s }, [u, o]) => {
        const n = left % o;
        left -= n;
        n && s.unshift(`${~~n}${u}`);
        return { left: ~~(left / o), s };
    },
    { left: ms, s: [] }
).s.join(" ");