I am writing an app in node.js and starting to do some advanced data manipulation now. One thing I have not found in the mongoDb docs was how to do group by count query.
So here is my solution. (nodejs code right out of my array utility "class")
// Arry to object with defined keys.
exports.groupCount = function(array, key){
var group = {};
array.forEach(function(d, i){
var keyName = d[key];
if(group[keyName]){
group[keyName].count++;
} else {
group[keyName] = {
count: 1
}
}
});
return group;
};