Getting an object from _.pluck with lo-dash/underscore

Question

I have an object structured like this:

var my_object = {
  first_item: {important_number: 4},
  second_item: {important_number: 6},
}

However, I would like an object structured like this:

{
  first_item: 4,
  second_item: 6,
}

I would have expected to be able to get this result with _.pluck:

_.pluck(my_object, "important_number")

But this gives me:

[0: 4, 1: 6]

Good, but I need the actual names of the objects. I fiddled around and ended up with this:

_.reduce(my_object, function(memo, val, key) {
  memo[key] = val.content;
  return memo;
}, {});

Which has the desired effect, but isn't as simple as I would like. Is there a better solution in underscore/lodash, or is this the best it will get?

Answer 1

In Lo-Dash you could also use _.transform, a more powerful alternative to _.reduce:

_.transform(my_object, function(memo, val, key) {
  memo[key] = val.important_number;
});

Answer 2

Actually what you're describing - that is "pluck for object values" - can be written as:

_.mapValues(my_object, "important_number")

See documentation of _.mapValues.

_.createCallback - which does the string to property magic - is used all over the place in Lo-Dash: search for "_.pluck" style callback.