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

The improvements by joyrexus on bergi's method don't take advantage of the underscore/lodash mixin system. Here it is as a mixin:

_.mixin({
  nest: function (collection, keys) {
    if (!keys.length) {
      return collection;
    } else {
      return _(collection).groupBy(keys[0]).mapValues(function(values) {
        return _.nest(values, keys.slice(1));
      }).value();
    }
  }
});