Assuming I have the following:
var array =
[
{\"name\":\"Joe\", \"age\":17},
{\"name\":\"Bob\", \"age\":17},
{\"name\":\"Carl\
i think you are looking for groupBy function (using Lodash)
_personsList = [{"name":"Joe", "age":17},
{"name":"Bob", "age":17},
{"name":"Carl", "age": 35}];
_uniqAgeList = _.groupBy(_personsList,"age");
_uniqAges = Object.keys(_uniqAgeList);
produces result:
17,35
jsFiddle demo:http://jsfiddle.net/4J2SX/201/