If you want to remove all falsey values then the most compact way is:
For Lodash 4.x and later:
_.pickBy({ a: null, b: 1, c: undefined }, _.identity);
>> Object {b: 1}
For legacy Lodash 3.x:
_.pick(obj, _.identity);
_.pick({ a: null, b: 1, c: undefined }, _.identity);
>> Object {b: 1}