function h3IndexToSplitLong(h3Index) {
    if (
        Array.isArray(h3Index) &&
        h3Index.length === 2 &&
        Number.isInteger(h3Index[0]) &&
        Number.isInteger(h3Index[1])
    ) {
        return h3Index;
    }
    if (typeof h3Index !== 'string' || INVALID_HEXIDECIMAL_CHAR.test(h3Index)) {
        return [0, 0];
    }
    const upper = parseInt(h3Index.substring(0, h3Index.length - 8), BASE_16);
    const lower = parseInt(h3Index.substring(h3Index.length - 8), BASE_16);
    return [lower, upper];
}
Convert an H3 index (64-bit hexidecimal string) into a "split long" - a pair of 32-bit ints
@param  {H3IndexInput} h3Index  H3 index to check
@return {SplitLong}             A two-element array with 32 lower bits and 32 upper bits