The current groupBy function only adds each Collection object to the returned hash only once.
In some case one might want to add the same object in multiple groups.
A concrete example is an object having an array property.
function addToGroup(result, value, key) {
if .isArray(key) { .each(key, function(k) { addToGroup(result, value, k); }); return; }
if (_.has(result, key)) result[key].push(value); else result[key] = [value];
});
_.groupBy = group(addToGroup);
I implemented this for my backbone collection as groupByMulti but that is rather cumbersome as I don't have access to the underscore internals, in particular the group function.
The current groupBy function only adds each Collection object to the returned hash only once. In some case one might want to add the same object in multiple groups.
A concrete example is an object having an array property.
Basically this means replacing:
.groupBy = group(function(result, value, key) { if (.has(result, key)) result[key].push(value); else result[key] = [value]; });
by
function addToGroup(result, value, key) { if .isArray(key) { .each(key, function(k) { addToGroup(result, value, k); }); return; } if (_.has(result, key)) result[key].push(value); else result[key] = [value]; });
_.groupBy = group(addToGroup);
I implemented this for my backbone collection as groupByMulti but that is rather cumbersome as I don't have access to the underscore internals, in particular the group function.