javascript - 过滤数组并获取第一个值作为唯一 id 的对象数组

Question

我有以下数组例如，我只需要返回唯一 ID，因为在这个数组中我有两次 id 1 和 3 我需要仅包含第一个 findigs id 的新数组，

在此示例中，前 3 个条目，我如何将其与映射/过滤器一起使用，而不是与常规 for 一起使用

var oData = [{
  id: 1,
  ListTypeGroupDescription: 2,
  test: 111,
  test2: 222
}, {
  id: 2,
  ListTypeGroupDescription: 4,
  test: 333,
  test2: 444
}, {
  id: 3,
  ListTypeGroupDescription: 6,
  test: 666,
  test2: 777
}, {
  id:1,
  ListTypeGroupDescription: 99,
  test: 666,
  test2: 777
}, {
  id: 3,
  ListTypeGroupDescription: 99,
  test: 666,
  test2: 777
}];


var data = oData.map(
  function(obj) {
    return obj.id;
  }
);

http://jsfiddle.net/5qu0j8g0/1/

map 仅返回 ID，但我需要所有对象

我需要这个新数组

var oNew = [{
  id: 1,
  ListTypeGroupDescription: 2,
  test: 111,
  test2: 222
}, {
  id: 2,
  ListTypeGroupDescription: 4,
  test: 333,
  test2: 444
}, {
  id: 3,
  ListTypeGroupDescription: 6,
  test: 666,
  test2: 777
}
]

Answer 1

您可以使用 Array#filter 进行过滤和一个临时哈希表 Object.create(null))(一个没有任何原型(prototype)的空对象)，位于使用 this 寻址的回调中。

The filter() method creates a new array with all elements that pass the test implemented by the provided function.

var oData = [{ id: 1, ListTypeGroupDescription: 2, test: 111, test2: 222 }, { id: 2, ListTypeGroupDescription: 4, test: 333, test2: 444 }, { id: 3, ListTypeGroupDescription: 6, test: 666, test2: 777 }, { id: 1, ListTypeGroupDescription: 99, test: 666, test2: 777 }, { id: 3, ListTypeGroupDescription: 99, test: 666, test2: 777 }],
    oNew = oData.filter(function (a) {
        if (!this[a.id]) {
            this[a.id] = true;
            return true;
        }
    }, Object.create(null));

console.log(oNew);

ES6

var oData = [{ id: 1, ListTypeGroupDescription: 2, test: 111, test2: 222 }, { id: 2, ListTypeGroupDescription: 4, test: 333, test2: 444 }, { id: 3, ListTypeGroupDescription: 6, test: 666, test2: 777 }, { id: 1, ListTypeGroupDescription: 99, test: 666, test2: 777 }, { id: 3, ListTypeGroupDescription: 99, test: 666, test2: 777 }],
    oNew = oData.filter((temp => a => !temp[a.id] && (temp[a.id] = true))(Object.create(null)));

console.log(oNew);