在 JS 中使用深层文字键减少对象数组

Question

我对使用 reduce 方法进行数组转换感到困惑。我不知道如何使用文字键处理嵌套对象。

为了带来一些好处，我将 post 一些我写的例子，它工作正常：

// consider flat array of objects
const names = [
{ name: "Jaden", sname: "Smith", age: 33 }, 
{ name: "Will", sname: "Smith", age: 12 },
{ name: "Jada", sname: "Smith", age: 29 }, 
{ name: "Jose", sname: "Varho", age: 21 },
{ name: "Josephina", sname: "Varho", age: 44 }, 
{ name: "Keanu ", sname: "Reeves", age: 44 }] ;

// suppose i need to transform that array to this shape:
/* {
    "Smith": {
        "Jaden": 33,
        "Will": 12,
        "Jada": 29
    },
    "Varho": {
        "Jose": 21,
        "Josephina": 44
    },
    "Reeves": {
        "Keanu ": 44
    }
}

*/

// this reducer do it's fine:
const shapeIt = (acc, item) => {
    console.log('acc:', JSON.stringify(acc));
    acc[item.sname] = { ...acc[item.sname], [item.name]: item.age }
    return acc
}

const transformShape= (arr) => {
    return arr.reduce((acc, item) => shapeIt(acc, item), {});
}

transformShape(names); //gives required shape

所以现在，让我们想象一下我有更复杂的数组，例如：

 const flatArray = [
{ "blockId": "first-block", "sectionId": "first-section", "fieldId": "_1", "value": "0" }, 
{ "blockId": "first-block", "sectionId": "first-section", "fieldId": "_2", "value": "1" }, 
{ "blockId": "first-block", "sectionId": "second-section", "fieldId": "_1", "value": "1" }, 
{ "blockId": "second-block", "sectionId": "first-section", "fieldId": "_1", "value": "1" }, 
{ "blockId": "second-block", "sectionId": "some-section", "fieldId": "_2", "value": "3" },
{ "blockId": "third-block", "sectionId": "other-section", "fieldId": "_1", "value": "3" }];

// and i strictly need to get this shape of object:

/* {
    "first-block": {
        "first-section": {
            "_1": "0",
            "_2": "1"
        },
        "second-section": {
            "_1": "1"
        }
    },
    "second-block": {
        "first-section": {
            "_1": "1"
        },
        "some-section": {
            "_2": "3"
        }
    },
    "third-block": {
        "other-section": {
            "_1": "3"
        }
    }
}
*/

此刻我正在写这种reduce函数。它有效，但它只给我块中每个部分的最后一个 fieldId 键。如果一个块中的部分有多个 fieldId - 它会丢失它。我正在观察一个累加器，发现只有具有不同 blockId、sectionId 的键被累加，但没有不同的 fieldId。


const shapeComplex = (acc, item) => {
    console.log('acc:', JSON.stringify(acc));
    acc[item.blockId] = { ...acc[item.blockId], [item.sectionId]: { [item.fieldId]: item.value } }

    return acc
}

const transformComplex = (arr) => {
    console.log('initialArr: ', arr)
    return arr.reduce((acc, item) => shapeComplex(acc, item), {});
}

transformComplex(flatArray); 
// it gives me shape with only last idField in same section and block:

/*
{
    "first-block": {
        "first-section": {
            "_1": "0"
        },
        "second-section": {
            "_1": "1"
        }
    },
    "second-block": {
        "first-section": {
            "_1": "1"
        },
        "some-section": {
            "_2": "3"
        }
    },
    "third-block": {
        "other-section": {
            "_1": "3"
        }
    }
}
*/

任何帮助，请。

Answer 1

您可以采用所需键的数组进行分组，并采用值或新对象进行下一级。

const
    data = [{ blockId: "first-block", sectionId: "first-section", fieldId: "_1", value: "0" }, { blockId: "first-block", sectionId: "first-section", fieldId: "_2", value: "1" }, { blockId: "first-block", sectionId: "second-section", fieldId: "_1", value: "1" }, { blockId: "second-block", sectionId: "first-section", fieldId: "_1", value: "1" }, { blockId: "second-block", sectionId: "some-section", fieldId: "_2", value: "3" }, { blockId: "third-block", sectionId: "other-section", fieldId: "_1", value: "3" }],
    keys = ['blockId', 'sectionId', 'fieldId'],
    result = data.reduce((r, o) => {
        keys.reduce(
            (q, k, i, { length }) => q[o[k]] ??= i + 1 === length ? o.value : {},
            r
        );
        return r;
    }, {});

console.log(result);

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方法是获取对象的所有值并将最后一项指定为嵌套最多的对象的值。

此方法依赖于每个对象中值的顺序。

const
    data = [{ blockId: "first-block", sectionId: "first-section", fieldId: "_1", value: "0" }, { blockId: "first-block", sectionId: "first-section", fieldId: "_2", value: "1" }, { blockId: "first-block", sectionId: "second-section", fieldId: "_1", value: "1" }, { blockId: "second-block", sectionId: "first-section", fieldId: "_1", value: "1" }, { blockId: "second-block", sectionId: "some-section", fieldId: "_2", value: "3" }, { blockId: "third-block", sectionId: "other-section", fieldId: "_1", value: "3" }],
    result = data.reduce((r, o) => {
        const
            values = Object.values(o),
            value = values.pop();
        values.reduce(
            (q, k, i, { length }) => q[k] ??= i + 1 === length ? value : {},
            r
        );
        return r;
    }, {});

console.log(result);

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Answer 2

您还需要复制最里面（部分）对象的属性（字段）：

const shapeComplex = (acc, item) => {
    console.log('acc:', JSON.stringify(acc));
    acc[item.blockId] = {
        ...acc[item.blockId],
        [item.sectionId]: {
            ...acc[item.blockId]?.[item.sectionId],
//          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            [item.fieldId]: item.value
        }
    };
    return acc
}

不过，我会建议始终在每个级别上使用对象传播

const shapeComplex = (acc, item) => {
    return {
        ...acc,
        [item.blockId]: {
            ...acc[item.blockId],
            [item.sectionId]: {
                ...acc[item.blockId]?.[item.sectionId],
                [item.fieldId]: item.value
            }
        }
    };
}

或使用突变：

const shapeComplex = (acc, {blockId, sectionId, fieldId, value}) => {
    const block = acc[blockId] ?? (acc[blockId] = {});
    const section = block[sectionId] ?? (block[sectionId] = {});
    section[fieldId] = value;
    return acc;
}

正如@Nina 在此处的回答中所示，您可以将其概括为任意深度的作业。

Answer 3

您可以执行以下操作，

const flatArray = [
{ "blockId": "first-block", "sectionId": "first-section", "fieldId": "_1", "value": "0" }, 
{ "blockId": "first-block", "sectionId": "first-section", "fieldId": "_2", "value": "1" }, 
{ "blockId": "first-block", "sectionId": "second-section", "fieldId": "_1", "value": "1" }, 
{ "blockId": "second-block", "sectionId": "first-section", "fieldId": "_1", "value": "1" }, 
{ "blockId": "second-block", "sectionId": "some-section", "fieldId": "_2", "value": "3" },
{ "blockId": "third-block", "sectionId": "other-section", "fieldId": "_1", "value": "3" }];


const shapeComplex = (acc, item) => {
    
    if(acc[item.blockId]) {
        acc[item.blockId] = { ...acc[item.blockId], [item.sectionId]: {...acc[item.blockId][item.sectionId], [item.fieldId]: item.value } }
    } else {
        acc[item.blockId] = { ...acc[item.blockId], [item.sectionId]: {[item.fieldId]: item.value } }
    }
    return acc
}

const transformComplex = (arr) => {
    
    return arr.reduce((acc, item) => shapeComplex(acc, item), {});
}

console.log(transformComplex(flatArray));

Answer 4

您正在从平面数据结构中创建一棵树。指定树层次结构（级别）和用于创建叶节点数据元素的属性。

示例：

    function treeFrom (arr, levels, name, value) {
      return arr.reduce( 
        (root,item) => 
        {          
          var node = root;
          for (let level of levels) /* descend to bottom tier */
          {
            levelvalue = item[level];
            if (! node[levelvalue]) node[levelvalue] = {};
            node = node[levelvalue];
          }
          node[item[name]] = item[value];

          return root;
        }
      , 
        {}
      )
    }
    
    console.log ( treeFrom(flatArray, ['blockId', 'sectionId'], 'fieldId', 'value') );

在 JS 中使用深层文字键减少对象数组

Reduce array of objects with deeply literals keys in JS

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