mongodb map-reduce to group by week

mongo_mapreduce_by_week.js

m = function() {
    var getWeek = function(d) {
        /*getWeek() was developed by Nick Baicoianu at MeanFreePath: http://www.meanfreepath.com */
        dowOffset = 1;
        var newYear = new Date(d.getFullYear(),0,1);
        var day = newYear.getDay() - dowOffset;
        day = (day >= 0 ? day : day + 7);
        var daynum = Math.floor((d.getTime() - newYear.getTime() - (d.getTimezoneOffset()-newYear.getTimezoneOffset())*60000)/86400000) + 1;
        var weeknum;
        if (day < 4) {
            weeknum = Math.floor((daynum+day-1)/7) + 1;
            if(weeknum > 52) {
                nYear = new Date(d.getFullYear() + 1,0,1);
                nday = nYear.getDay() - dowOffset;
                nday = nday >= 0 ? nday : nday + 7;
                weeknum = nday < 4 ? 1 : 53;
            }
        } else {
            weeknum = Math.floor((daynum+day-1)/7);
        }
        return weeknum;
    };
    var data = {};
    data[this.metadata.serviceref] = 1;
    emit(getWeek(this.metadata.publishdate), data);
};

r = function(key, values){
    var by_service = {};  
    values.forEach(function(service_counts){
        // Add {cg:1, gp:1} to {cg:11, gp:22}
        for (serviceref in service_counts) {
            var count = service_counts[serviceref];
            by_service[serviceref] = by_service[serviceref] || 0;
            by_service[serviceref] += count;
        };
    });
    return by_service;
};


// USAGE
use publications
res = db.reports.files.mapReduce(m, r, {
    query: {'metadata.publishdate': {$gte: new Date(2009, 03, 04), $lte:new Date(2010, 03, 04)}}
})
db[res.result].find()

can you please provide a input json and output json??