Lodash differenceBy澄清

Question

我有两个对象数组，我想通过newData找到oldData数组和identifier数组之间的区别，显示差异，其中oldData的标识符与newData数组不同，下面是我的数组：

const newData = [
    {
        "extras": {},
        "identifier": "13",
        "latitude": 39.13063,
        "loiteringDelay": 1000,
        "longitude": -86.58286,
        "notifyOnDwell": false,
        "notifyOnEntry": true,
        "notifyOnExit": true,
        "radius": 30,
    },
    {
        "extras": {},
        "identifier": "18",
        "latitude": 39.13063,
        "loiteringDelay": 1000,
        "longitude": -86.58286,
        "notifyOnDwell": false,
        "notifyOnEntry": true,
        "notifyOnExit": true,
        "radius": 30,
    }

]

const oldData = [
    {
        "identifier": "13",
        "latitude": 39.13063,
        "loiteringDelay": 1000,
        "longitude": -86.58286,
        "notifyOnDwell": false,
        "notifyOnEntry": true,
        "notifyOnExit": true,
        "radius": 30,
    },
    {
        "identifier": "12",
        "latitude": 39.13063,
        "loiteringDelay": 1000,
        "longitude": -86.58286,
        "notifyOnDwell": false,
        "notifyOnEntry": true,
        "notifyOnExit": true,
        "radius": 30,
    }
]

我在这里做的是：

let testDifference = _.differenceBy(newData, oldData, "identifier")

我的期望，我会得到

[
    {
        "identifier": "12",
        "latitude": 39.13063,
        "loiteringDelay": 1000,
        "longitude": -86.58286,
        "notifyOnDwell": false,
        "notifyOnEntry": true,
        "notifyOnExit": true,
        "radius": 30,
    },
]

实际上，我得到的是空数组，我做错了什么？如何使它正确工作？

Answer 1

我认为您只需要将前两个参数切换到differenceBy，就可以得到预期的结果。您可以将其看作是第一个数组项()，除了(第二个数组项)。

const newData = [{
  "extras": {},
  "identifier": "13",
  "latitude": 39.13063,
  "loiteringDelay": 1000,
  "longitude": -86.58286,
  "notifyOnDwell": false,
  "notifyOnEntry": true,
  "notifyOnExit": true,
  "radius": 30,
}]

const oldData = [{
    "identifier": "13",
    "latitude": 39.13063,
    "loiteringDelay": 1000,
    "longitude": -86.58286,
    "notifyOnDwell": false,
    "notifyOnEntry": true,
    "notifyOnExit": true,
    "radius": 30,
  },
  {
    "identifier": "12",
    "latitude": 39.13063,
    "loiteringDelay": 1000,
    "longitude": -86.58286,
    "notifyOnDwell": false,
    "notifyOnEntry": true,
    "notifyOnExit": true,
    "radius": 30,
  }
];

let whatDelete = _.differenceBy(oldData, newData, "identifier");

console.log(whatDelete);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

​