Underscore.js: create a map out of list of objects using a key found in the object

Question

I am using the excellent Underscore.js library. I have a specific task which I can do fine using JavaScript or jQuery but was wondering if there was some sort of abstraction avaialable in Underscore that I was missing out on.

Essentially I have an object like so -

var some_object_array = [{id: "a", val: 55}, {id: "b", val: 1}, {id: "c", val: 45}]; 

I want to convert this into -

var some_map = {"a": {id: "a", val: 55}, "b": {id: "b", val: 1}, "c": {id: "c", val: 45}}; 

I know that I can use _.groupBy(some_object_array, "id"). But this returns a map like so -

var some_grouped_map = {"a": [{id: "a", val: 55}], "b": [{id: "b", val: 1}], "c": [{id: "c", val: 45}]}; 

Note that this does what it is advertised to do. But I was hoping to get some_map without iterating over the objects myself.

Any help appreciated.

Answer 1

For what it's worth, since underscore.js you can now use _.object()

var some_map = _.object(_.map(some_object_array, function(item) {    return [item.id, item] })); 

Answer 2

for your case, you should use the indexBy function:

var some_object_array = [{id: "a", val: 55}, {id: "b", val: 1}, {id: "c", val: 45}];  var some_grouped_map = _.indexBy(some_object_array, 'id');