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如何从 JS 数组中过滤数据并创建另一个 JS 数组

2020-10-28
93
javascript

我想从 JS 数组中过滤数据并创建另一个 JS 数组。我解释了以下场景。

有两个 JS 数组。它们是 arr1 和 arr2 

const arr1 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}];

const arr2 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}, 
{
  code: "vvg",
  dis: "cont15",
  note: "Note for cont15"
}];

我们可以在 arr2[1].dis 和 arr2[2].note 和 arr2[4].note 中进行更改。我在下面提到过 

const arr2 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2 new",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "New Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}, 
{
  code: "VVG",
  dis: "cont15",
  note: "Note for cont15 changed"
}];

一旦我更改了 arr2 ，我想将其与 arr1 进行比较并创建 new_arr 并将所有更改的元素推送到 new_arr 。比较应该使用 code 完成。因为 code: "VVG" 有变化。但它不应该包含在新数组中。因为 code: "VVG" 不在 arr1 中。 

Expected-output :

[
  {
    code: "AAW",
    dis: "cont2 new",
    note: "Note for cont2"
  },
  {
    code: "TTR",
    dis: "cont5",
    note: "New Note for cont5"
  }
]

尝试的代码： 

const codesss = new Set(arr1.map(({ code }) => code));
const  new_arr = arr2.filter(({ code }) => !codesss.has(code));

console.log(new_arr);

当前输出： 

[
  {
    "code": "VVG",
    "dis": "cont15",
    "note": "Note for cont15 changed"
  }
]

我的 当前输出 不是 预期输出 。请帮我解决这个问题。

2个回答

首先，使用 Array.prototype.reduce ，您可以使用 code 变量作为 key 从 arr1 构建新对象。

基于该对象，您可以使用 Array.prototype.filter 过滤所需的对象。 

const arr1 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}];

const arr2 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2 new",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "New Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}, 
{
  code: "VVG",
  dis: "cont15",
  note: "Note for cont15 changed"
}];

const arr1Obj = arr1.reduce((acc, cur) => {
  acc[cur.code] = cur;
  return acc;
}, {});

const result = arr2.filter((item) => arr1Obj[item.code] && !(arr1Obj[item.code].dis === item.dis && arr1Obj[item.code].note === item.note));
console.log(result);
Derek Wang
2020-10-28
const arr1 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}];

const arr2 = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}, 
{
  code: "vvg",
  dis: "cont15",
  note: "Note for cont15"
}];

const arr2Changed = [
{
  code: "XXY",
  dis: "cont1",
  note: "Note for cont1"
}, 
{
  code: "AAW",
  dis: "cont2 new",
  note: "Note for cont2"
}, 
{
  code: "TTR",
  dis: "cont5",
  note: "New Note for cont5"
}, 
{
  code: "MMN",
  dis: "cont10",
  note: "Note for cont10"
}, 
{
  code: "VVG",
  dis: "cont15",
  note: "Note for cont15 changed"
}];

const arr1Codes = {};
const newArray = [];
arr1.map(i => arr1Codes[i.code] = 1);
arr2Changed.map((item, index) => {
  const arr2Item = arr2[index];
  if (arr1Codes[arr2Item.code] && (arr2Item.dis !== item.dis || arr2Item.note !== item.note)) {
    newArray.push(item);
  }
});

console.log(newArray);
Aison
2020-10-28