A map reduce function that count the tags in a gist

tags-counter.js

use gistcube

map = function() {
    if (!this.tags) {
        return;
    }

    for (index in this.tags) {
        emit(this.tags[index], 1);
    }
};

reduce = function(previous, current) {
    var count = 0;

    for (index in current) {
        count += current[index];
    }

    return count;
}; 
 
result = db.runCommand({
  "mapreduce" : "gists",
  "map" : map,
  "reduce" : reduce,
  "out" : "tags"});

db.tags.find()