javascript - 从 AngularJS 中的对象访问所有嵌套值的最快方法

Question

在 AngularJS 中，我有一个来自 JSON API 调用的数千条记录的对象。我需要从每个记录(“主题”)中创建一个仅包含一个特定键的新数组，从而仅生成一组唯一值。 foreach 循环是执行此操作的唯一方法吗？例如:

数据数组(arr):

{
"id": 1,
"number": 2,
"section": "xx",
"importance": "high",
"applicability": "General",
"text": "some text here",
"topic": 
    {
        "id": 30,
        "title": "Gender and Diversity"
    }
 },
{
"id": 2,
"number": 2.1,
"section": "xx",
"importance": "high",
"applicability": "General",
"text": "some text here",
"topic": 
    {
        "id": 31,
        "title": "Health and Safety"
    }
 }, ...

我想要一个仅包含数千条记录中的主题的数组，如下所示:

"topic": 
{
    "id": 30,
    "title": "Gender and Diversity"
},
"topic": 
{
    "id": 31,
    "title": "Health and Safety"
},..

是否有比我目前拥有的更好(更快)的方法来创建此列表，即带有 if 语句的 foreach 循环，后跟唯一值的过滤器？:

var topics = function (arr) {
            var topics = [];
            angular.forEach(arr.data, function (ts) {
                angular.forEach(ts.topic, function (t) {
                    if (t.title) {
                        this.push(t);
                    }
                }, topics);

            });

            // Filter the unique values
            var elementId = [];

            var uniqueTopics = topics.filter(el => {
                if (elementId.indexOf(el.id) === -1) {
                    // If not present in array, then add it
                    elementId.push(el.id);
                    return true;
                } else {
                    // Already present in array, don't add it
                    return false;
                }
            });

            return uniqueTopics;

        };

Answer 1

这可能会有所帮助。

var data = [
{
"id": 1,
"number": 2,
"section": "xx",
"importance": "high",
"applicability": "General",
"text": "some text here",
"topic": 
    {
        "id": 30,
        "title": "Gender and Diversity"
    }
 },
{
"id": 2,
"number": 2.1,
"section": "xx",
"importance": "high",
"applicability": "General",
"text": "some text here",
"topic": 
    {
        "id": 31,
        "title": "Health and Safety"
    }
 }
];

console.log(
  data.map(d => { return { "topic": d.topic }; })
);

var data = [
    {
    "id": 1,
    "number": 2,
    "section": "xx",
    "importance": "high",
    "applicability": "General",
    "text": "some text here",
    "topic": 
        {
            "id": 30,
            "title": "Gender and Diversity"
        }
     },
    {
    "id": 2,
    "number": 2.1,
    "section": "xx",
    "importance": "high",
    "applicability": "General",
    "text": "some text here",
    "topic": 
        {
            "id": 31,
            "title": "Health and Safety"
        }
     }
    ];

    console.log(
      data.map(d => d.topic)
    );