Underscore.js implementation of Cartesian Product

gistfile1.js

function cartesianProductOf(){
    return _.reduce(arguments, function(mtrx, vals){
        return _.reduce(vals, function(array, val){
            return array.concat(
                _.map(mtrx, function(row){ return row.concat(val); })
            );
        }, []);
    }, [[]]);
}

Thanks! You should make innermost clause:

return row.concat([val]);

otherwise if someone (like me) is trying to use this on arrays of arrays, JS unwelcomely flattens the array. (And it's just as safe this way for when you're not passing arrays)