Question

在lodash中，我想将一个对象数组转换为一个包含每个属性数组的对象。

我有一个对象数组：

var students = [{
    name: 'A',
    idNo: 1,
    marks: {
        math: 98,
        sci: 97,
        eng: 89
    }
}, {
    name: 'B',
    idNo: 2,
    marks: {
        math: 88,
        sci: 87,
        eng: 79
    }
}, {
    name: 'C',
    idNo: 3,
    marks: {
        math: 87,
        sci: 98,
        eng: 91
    }
}]

我想像这样组合/重塑它们：

{
    name: [A, B, C],
    idNo: [1, 2, 3],
    marks: [{
            math: 98,
            sci: 97,
            eng: 89
        }, {

            math: 88,
            sci: 87,
            eng: 79            
    }, {
            math: 87,
            sci: 98,
            eng: 91
        }
    }]
}

我希望这完全是用lodash或js内置函数完成的，没有任何循环。

编辑：我已经按照Nenad的建议实施了一个解决方案。我想在lodash中使用实用程序功能。

Answer 1

您可以使用lodash的mapValues功能：

var result = _.mapValues(students[0], (value, key) => _.map(students, key));

mapValues创建一个对象，其键作为第一个参数传递给它的对象。在这里，我们传递学生数组students[0]中的第一个对象，因此mapValues返回的对象将如下所示：

{
    name: ....,
    idNo: ....,
    marks: ....
}

每个键的值由作为第二个参数传递给mapValues的函数确定。 mapValues将为每个键调用此函数并传递值和键。我们对该值不感兴趣，但该密钥用于获取该密钥的student数组中的所有值（通过使用密钥作为第二个参数调用map）。

＆＃13;

var students = [{
    name: 'A',
    idNo: 1,
    marks: {
        math: 98,
        sci: 97,
        eng: 89
    }
}, {
    name: 'B',
    idNo: 2,
    marks: {
        math: 88,
        sci: 87,
        eng: 79
    }
}, {
    name: 'C',
    idNo: 3,
    marks: {
        math: 87,
        sci: 98,
        eng: 91
    }
}]


var result = _.mapValues(students[0], (value, key) => _.map(students, key));

document.getElementById('result').textContent = JSON.stringify(result);

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

<p>
  <pre id="result"></pre>
</p>

＆＃13;

Answer 2

您可以使用带有扩展运算符的_.mergeWith()将数组中的所有对象合并到一个新对象：

＆＃13;

const students = [{"name":"A","idNo":1,"marks":{"math":98,"sci":97,"eng":89}},{"name":"B","idNo":2,"marks":{"math":88,"sci":87,"eng":79}},{"name":"C","idNo":3,"marks":{"math":87,"sci":98,"eng":91}}];

const result = _.mergeWith({}, ...students, (objValue, srcValue) => 
  (objValue || []).concat(srcValue));

console.log(result);

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>

＆＃13;

在较旧的浏览器中，您可以将所有参数连接到单个数组，并使用_.spread()：

＆＃13;

var students = [{"name":"A","idNo":1,"marks":{"math":98,"sci":97,"eng":89}},{"name":"B","idNo":2,"marks":{"math":88,"sci":87,"eng":79}},{"name":"C","idNo":3,"marks":{"math":87,"sci":98,"eng":91}}];
                                          
var result = _.spread(_.mergeWith)([{}].concat(students, function(objValue, srcValue){
  return (objValue || []).concat(srcValue);
}));

console.log(result);

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>

＆＃13;

Answer 3

您可以使用reduce()和forEach()来获得所需的结果。

＆＃13;

var students = [{"name":"A","idNo":1,"marks":{"math":98,"sci":97,"eng":89}},{"name":"B","idNo":2,"marks":{"math":88,"sci":87,"eng":79}},{"name":"C","idNo":3,"marks":{"math":87,"sci":98,"eng":91}}];

var result = students.reduce(function(r, e) {
  Object.keys(e).forEach(function(k) {
    if (!r[k]) {
      r[k] = [];
    }
    r[k].push(e[k])
  })
  return r;
}, {})

console.log(result)

＆＃13;

Answer 4

您可以使用单个reduce来完成;

＆＃13;

var students = [{
    name: 'A',
    idNo: 1,
    marks: {
        math: 98,
        sci: 97,
        eng: 89
    }
}, {
    name: 'B',
    idNo: 2,
    marks: {
        math: 88,
        sci: 87,
        eng: 79
    }
}, {
    name: 'C',
    idNo: 3,
    marks: {
        math: 87,
        sci: 98,
        eng: 91
    }
}],
     result = students.reduce((p,c) => (p.name.push(c.name), p.idNo.push(c.idNo), p.marks.push(c.marks), p), {name:[], idNo:[], marks:[]});
console.log(result);

＆＃13;

Answer 5

使用_.mergeWith

的另一个lodash示例

＆＃13;

var students = [{ name: 'A', idNo: 1, marks: { math: 98, sci: 97, eng: 89 } }, { name: 'B', idNo: 2, marks: { math: 88, sci: 87, eng: 79 } }, { name: 'C', idNo: 3, marks: { math: 87, sci: 98, eng: 91 } }],
    result = {};

    _.forEach(students, v => _.mergeWith(result, v, (o, s) => !_.isArray(o) ? [s] : o.concat(s)));

console.log(result);

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

＆＃13;

Answer 6

.reduce(collection, [iteratee=.identity], [accumulator])的另一个lodash示例。

collection (Array|Object)：要迭代的集合。
[iteratee=_.identity] (Function)：每次迭代调用的函数。
[accumulator] (*)：初始值。

代码：

var students = [{name: 'A', idNo: 1, marks: { math: 98, sci: 97, eng: 89}}, {name: 'B', idNo: 2, marks: { math:88,  sci: 87,  eng: 79}}, {name: 'C', idNo: 3, marks: { math: 87, sci: 98, eng: 91}}],
    obj = _.reduce(students, function(o, item) {
      o.name.push(item.name);
      o.idNo.push(item.idNo);
      o.marks.push(item.marks);
      return o;
    }, {name: [], idNo: [], marks: []});

console.log(obj);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

lodash：组合对象数组

6 个答案: