Underscore mixin that takes a list and splits it into multiple lists, where each list is n elements long

groupsOf.js

_.mixin({
    groupsOf: function(list, num) {
        if (!_.isArray(list)) {
            list = _.toArray(list);
        }
        var result = [];
        while (list.length) {
            result.push(list.splice(0, num));
        }
        return result;
    }
});

usageExample.js

_.groupsOf([1, 2, 3, 4, 5, 6, 7], 3); // returns [ [1,2,3], [4,5,6], [7] ]

_.groupsOf({
    valA: {
        firstName: "George",
        lastName: "Washington"
    },
    valB: {
        firstName: "John",
        lastName: "Adams"
    },
    valC: {
        firstName: "Thomas",
        lastName: "Jefferson"
    },
    valD: {
        firstName: "Aaron",
        lastName: "Burr"
    },
    valE: {
        firstName: "James",
        lastName: "Madison"
    },
    valF: {
        firstName: "George",
        lastName: "Clinton"
    },
    valG: {
        firstName: "James",
        lastName: "Monroe"
    },
    valH: {
        firstName: "Daniel",
        lastName: "Tompkins"
    }
}, 2);
/* 
    above function call returns:
    [
        [{"firstName":"George","lastName":"Washington"},{"firstName":"John","lastName":"Adams"}],   
        [{"firstName":"Thomas","lastName":"Jefferson"},{"firstName":"Aaron","lastName":"Burr"}],
        [{"firstName":"James","lastName":"Madison"},{"firstName":"George","lastName":"Clinton"}],
        [{"firstName":"James","lastName":"Monroe"},{"firstName":"Daniel","lastName":"Tompkins"}]
    ]

*/