Underscore.js groupBy multiple values

Question

Using Underscore.js, I\'m trying to group a list of items multiple times, ie

Group by SIZE then for each SIZE, group by CATEGORY...

http://jsfiddle.net/ricky

Answer 1

An example with lodash and mixin

_.mixin({
'groupByMulti': function (collection, keys) {
if (!keys.length) {
 return collection;
 } else {
  return _.mapValues(_.groupBy(collection,_.first(keys)),function(values) {
    return _.groupByMulti(values, _.rest(keys));
  });
}
}
});