function parseRetryAfterHeader(header, now) {
    if (now === void 0) { now = Date.now(); }
    var headerDelay = parseInt("" + header, 10);
    if (!isNaN(headerDelay)) {
        return headerDelay * 1000;
    }
    var headerDate = Date.parse("" + header);
    if (!isNaN(headerDate)) {
        return headerDate - now;
    }
    return DEFAULT_RETRY_AFTER;
}
Extracts Retry-After value from the request header or returns default value
@param header string representation of 'Retry-After' header
@param now current unix timestamp