Javascript - 仅返回对象数组中的唯一值

Question

我有一个对象数组，我只想根据它们的对象 ID 返回唯一的对象。

我试图在现有数组中循环，data然后查找元素是否已经添加到新创建的数组中arr，该数组应该只包含唯一值，但它对我不起作用，我相信我在这里或那里遗漏了一些东西.

这是当前数组：

          [
        {
          "objectId": "WMtwbyhFI6",
          "cuisineNameEn": "Cafe",
          "ordersNo": 20,
          "hidden": false
        },
        {
          "objectId": "QJSNTMpq5F",
          "ordersNo": 24,
          "cuisineNameEn": "Italian",
          "hidden": false
        },
        {
          "objectId": "iLXKswFRGa",
          "ordersNo": 5,
          "cuisineNameEn": "Japanese",
          "hidden": true
        },
        {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        },
        {
          "objectId": "QJSNTMpq5F",
          "ordersNo": 24,
          "cuisineNameEn": "Italian",
          "hidden": false
        },
        {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        },
        {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false,
        },
        {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        },
         {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        },
         {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        },
        {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        }
      ]

但是，这就是我想要返回的内容：

 [
        {
          "objectId": "WMtwbyhFI6",
          "cuisineNameEn": "Cafe",
          "ordersNo": 20,
          "hidden": false
        },
        {
          "objectId": "iLXKswFRGa",
          "ordersNo": 5,
          "cuisineNameEn": "Japanese",
          "hidden": true
        },
        {
          "objectId": "Db0MeihpJE",
          "ordersNo": 6,
          "cuisineNameEn": "Fast Food",
          "hidden": false
        },
        {
          "objectId": "QJSNTMpq5F",
          "ordersNo": 24,
          "cuisineNameEn": "Italian",
          "hidden": false
        }
      ]

我尝试了以下方法：

 var arr = [];
  data.forEach((el)=>{
  if (arr.indexOf(el.objectId) === -1) {
    arr.push(el)
  }
 })

然而，它没有用。

Answer 1

使用reduce()方法：

data.reduce((acc, x) =>
   acc.concat(acc.find(y => y.ordersNo === x.ordersNo) ? [] : [x])
 , []);

reduce遍历数组，对于每个元素，它使用累加器（前一次调用的返回值）和当前元素调用提供的函数。concat如果当前元素尚不存在，则将当前元素添加到累加器中。find通过比较ordersNo属性检查当前元素是否存在于累加器中。

演示：

data.reduce((acc, x) =>
   acc.concat(acc.find(y => y.ordersNo === x.ordersNo) ? [] : [x])
 , []);