backbone.js - 如何从集合中查找不同值的数量

Question

假设我有一个像这样的集合:

  {
     "id": 1,
     "name": "jonas",
  },
  {
     "id": 2,
     "name": "jonas",
  },
  {
     "id":3,
     "name": "smirk",
  }

如何得到 :

不同名称的数量，例如在这种情况下，2

不同的名字，在这种情况下，乔纳斯和傻笑？

Answer 1

使用一些 Backbone 和 Underscore 魔法，结合 collection.pluck 和 _.uniq :

pluck collection.pluck(attribute)
Pluck an attribute from each model in the collection. Equivalent to calling map, and returning a single attribute from the iterator.

uniq _.uniq(array, [isSorted], [iterator])
Produces a duplicate-free version of the array, using === to test object equality.
[...]

var c = new Backbone.Collection([
    {id: 1, name: "jonas"},
    {id: 2, name: "jonas"},
    {id: 3, name: "smirk"}
]);

var names = _.uniq(c.pluck('name'));
console.log(names.length);
console.log(names);

和一个演示 http://jsfiddle.net/nikoshr/PSFXg/