比较两个对象数组，如果不存在则推送

Question

我有下面两个对象数组

var array_1 = [{"Date": "2020-04-01", "Item" : 001},{"Date": "2020-04-03", "Item" : 002}]
var base_array = [{"Date": "2020-04-01", "Item" : null}, {"Date": "2020-04-02", "Item" : null}, 
                  {"Date": "2020-04-04", "Item" : null}]

我打算修改array_1如下

 var array_1 = [{"Date": "2020-04-01", "Item" : 001},
                {"Date": "2020-04-02", "Item" : null},
                {"Date": "2020-04-03", "Item" : 002},
                {"Date": "2020-04-04", "Item" : null}]

由于 array_1 中不存在日期“2020-04-02”和“2020-04-04”，因此这些日期应该以“item”为空来推送，并且不应推送“2020-04-01”，因为它已经存在于array_1 中。

我已经尝试在每个循环之后执行，但无法继续

小提示：base_array 将始终包含比 array_1 更多的值。这就是为什么我使用 base_array 作为我的初始循环

$.each(base_array , function (key,bvalue) {

    $.each(array_1, function (key,value) {
          if(bvalue.Date != value.Date){

               array_1.push({"Date" : value.Date, "Item": value.Item})
          }
    })
})

Answer 1

您可以在base_array 上使用Array.reduce()，将array_1 作为初始值传递，并且只添加来自base_array 的值，其中Date 尚不存在于进位值中：

var array_1 = [{
  "Date": "2020-04-01",
  "Item": 001
}, {
  "Date": "2020-04-03",
  "Item": 002
}];
var base_array = [{
    "Date": "2020-04-01",
    "Item": null
  }, {
    "Date": "2020-04-02",
    "Item": null
  },
  {
    "Date": "2020-04-04",
    "Item": null
  }
];

array_1 = base_array.reduce((c, v) => c.concat(c.some(e => e.Date == v.Date) ? [] : [v]), array_1);
console.log(array_1);

Answer 2

您可以获取一个哈希表，将对象分配给相同的日期并获取一个对象数组。

最后按Date对数组进行排序。

var array_1 = [{ Date: "2020-04-01", Item: "001" }, { Date: "2020-04-03", Item: "002" }],
    base_array = [{ Date: "2020-04-01", Item: null }, { Date: "2020-04-02", Item: null }, { Date: "2020-04-04", Item: null }],
    result = Object
        .values([...base_array, ...array_1].reduce((r, o) => (r[o.Date] = o, r), {}))
        .sort(({ Date: a }, { Date: b }) => a > b || -(a < b))

console.log(result);

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Answer 3

我不确定订单对您是否重要，但如果不重要，这里有一个解决方案

// Keep track of all dates already present in `array_1`.
let array_1_dates = new Set(array_1.map(array_1_elem => array_1_elem.Date));

// Push elements from `base_array` that are not in `array_1`.
for (let base_array_elem of base_array) {
  if (!array_1_dates.has(base_array_elem.Date)) {
    array_1.push(base_array_elem);
  }
}

Answer 4

首先使用filter 从base_array 中删除array_1 上已经存在的元素。然后concat。

var array_1 = [{"Date": "2020-04-01", "Item" : 001},{"Date": "2020-04-03", "Item" : 002}]
var base_array = [{"Date": "2020-04-01", "Item" : null}, {"Date": "2020-04-02", "Item" : null}, {"Date": "2020-04-04", "Item" : null}]
                  
var filtered = base_array.filter(({Date}) => !array_1.some(el => el.Date == Date));
var result = array_1.concat(filtered);
console.log(result);

Answer 5

您可以使用简单的循环并通过比较找到插入位置。

var array_1 = [{
  "Date": "2020-04-01",
  "Item": 001
}, {
  "Date": "2020-04-03",
  "Item": 002
}]
var base_array = [{
    "Date": "2020-04-01",
    "Item": null
  }, {
    "Date": "2020-04-02",
    "Item": null
  },
  {
    "Date": "2020-04-04",
    "Item": null
  }
]

// iterate over second array
base_array.forEach(el => {
  for (let i = 0; i < array_1.length; i++) {
    // if value found return
    if (array_1[i].Date === el.Date) return;
    // if position found, insert and return
    if (array_1[i].Date > el.Date) {
      array_1.splice(i, 0, el);
      return
    }
  }
  // or insert at the end of the array
  array_1.push(el);
})

console.log(array_1);

注意： 假设第一个数组总是有序的。

---

更新：或者如果顺序可能发生变化并且您不想在最后添加它们，那么您可以使用Array#some 和Array#filter 方法。

var array_1 = [{
  "Date": "2020-04-01",
  "Item": 001
}, {
  "Date": "2020-04-03",
  "Item": 002
}]
var base_array = [{
    "Date": "2020-04-01",
    "Item": null
  }, {
    "Date": "2020-04-02",
    "Item": null
  },
  {
    "Date": "2020-04-04",
    "Item": null
  }
]

array_1.push(...base_array.filter(o => array_1.every(o1 => o1.Date !== o.Date)))

console.log(array_1);