Question

我想创建自己的函数，该函数将对象数组作为参数和要分组的键，然后根据指定的分组键创建索引的键值对。

例如：

var iris = [
  {"Sepal_Length":1,"Sepal_Width":3.2, "Species":"setosa"},
{"Sepal_Length":1,"Sepal_Width":3.3, "Species":"viridis"},
{"Sepal_Length":1,"Sepal_Width":3.5, "Species":"virsicolor"},
{"Sepal_Length":2,"Sepal_Width":3.7, "Species":"setosa"},
{"Sepal_Length":1,"Sepal_Width":3.2, "Species":"viridis"},
{"Sepal_Length":2,"Sepal_Width":3.8, "Species":"virsicolor"}]

我想创建一个函数，该函数将允许我按物种分组以生成具有索引的新数组：

var iris = [
  {"Sepal_Length":1,"Sepal_Width":3.2,"Species":"setosa", "index":1},
{"Sepal_Length":1,"Sepal_Width":3.3,"Species":"viridis", "index":2},
{"Sepal_Length":1,"Sepal_Width":3.5,"Species":"virsicolor", "index":3},
{"Sepal_Length":2,"Sepal_Width":3.7,"Species":"setosa", "index":1},
{"Sepal_Length":1,"Sepal_Width":3.2,"Species":"viridis", "index": 2},
{"Sepal_Length":2,"Sepal_Width":3.8,"Species":"virsicolor", "index": 3}]

我尝试使用map和forEach，但我对JS较新，因此感到有些困惑。任何帮助表示感谢，非常感谢！

Answer 1

如果没有为此组设置索引，则可以将一个对象用作索引，并增加最大值。

var iris = [{ Sepal_Length: 1, Sepal_Width: 32, Species: "setosa" }, { Sepal_Length: 1, Sepal_Width: 32, Species: "viridis" }, { Sepal_Length: 1, Sepal_Width: 32, Species: "virsicolor" }, { Sepal_Length: 2, Sepal_Width: 32, Species: "setosa" }, { Sepal_Length: 1, Sepal_Width: 32, Species: "viridis" }, { Sepal_Length: 2, Sepal_Width: 32, Species: "virsicolor" }],
    indices = Object.create(null), 
    max = 0,
    result = iris.map(o => Object.assign(
        {},
        o,
        { index: indices[o.Species] = indices[o.Species] || ++max }
   ));

console.log(result);

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Answer 2

您可以创建一个map对象，该对象的每个唯一值都是键，而索引是值。 Destructure和key分别获得属性的值和rest。如果map对象已经具有密钥，请使用它。否则，增加索引并向map添加新密钥。

var iris = [{Sepal_Length:1,Sepal_Width:3.2,Species:"setosa"},{Sepal_Length:1,Sepal_Width:3.2,Species:"viridis"},{Sepal_Length:1,Sepal_Width:3.2,Species:"virsicolor"},{Sepal_Length:2,Sepal_Width:3.2,Species:"setosa"},{Sepal_Length:1,Sepal_Width:3.2,Species:"viridis"},{Sepal_Length:2,Sepal_Width:3.2,Species:"virsicolor"}];

function addIndex(array, key) {
  let map = {}, index = 0;
  
  return array.map(o => {
    const value = o[key];
    map[value] = map[value] || ++index;
    return { ...o, index: map[value] }
  })
}

console.log(addIndex(iris, 'Species'))
console.log(addIndex(iris, 'Sepal_Length'))

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如果要按多个键分组，则可以创建一个字符串，该字符串是由|分隔的那些键的值的组合。

keys.map(k => o[k]).join('|')

现在，map对象将具有参数中提到的键的每个唯一组合。这是一个片段：

var iris = [{Sepal_Length:1,Sepal_Width:3.2,Species:"setosa"},{Sepal_Length:1,Sepal_Width:3.2,Species:"viridis"},{Sepal_Length:1,Sepal_Width:3.2,Species:"virsicolor"},{Sepal_Length:2,Sepal_Width:3.2,Species:"setosa"},{Sepal_Length:1,Sepal_Width:3.2,Species:"viridis"},{Sepal_Length:2,Sepal_Width:3.2,Species:"virsicolor"}];

function addIndex(array, keys) {
  let map = {}, index = 0;
  
  return array.map(o => {
    const partial = keys.map(k => o[k]).join('|');
    map[partial] = map[partial] || ++index;
    return { ...o, index: map[partial] }
  })
}

console.log(addIndex(iris, ['Species', 'Sepal_Length']))

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Answer 3

您可以使用所有groupId创建一个对象，然后--

const groupObj = {
    "setosa": "1",
    "viridis": "2",
    "virsicolor": "3",
};

iris.map((item) => {
    item['index'] = groupObj[item.Species];
});

console.log(iris);

按组为对象数组创建索引列

3 个答案: