json数组的值的总和答案

【问题标题】：sum of the values of the json arrayjson数组的值的总和
【发布时间】：2017-10-08 09:04:03
【问题描述】：

下面是我的 json 响应生成的数组

 [
        {
    "id": "name1",
    "c1": "10",
    "c2": "20",
    "c3": "30",
    "c4": "40"
        },
    {
    "id": "name2",
    "c1": "20",
    "c2": "40",
    "c3": "25",
    "c4": "38"
        }
    ]

我需要计算除第一个字段之外的字段值的总和，因为我得到的第一个是字段名称

结果数组：

  [
    "c1": 30,
    "c2": 60,
    "c3": 55,
    "c4": 78
      ]

【问题讨论】：

Better way to sum a property value in an array (Using Angularjs)的可能重复

标签： json ecmascript-6 lodash

【解决方案1】：

仅使用 ES6，您可以使用 2 个 Array#reduce 循环来做到这一点：

const data = [{"id":"name1","c1":"10","c2":"20","c3":"30","c4":"40"},{"id":"name2","c1":"20","c2":"40","c3":"25","c4":"38"}];

const result = data.reduce((sums, obj) => Object.keys(obj).reduce((s, k) => {    
    k === 'id' || (s[k] = (s[k] || 0) + +obj[k]);
    
    return s;
}, sums), {});

console.log(result);

或者您可以使用 lodash 的 _.mergeWith() 和 _.omit() 结果中的“id”：

const data = [{"id":"name1","c1":"10","c2":"20","c3":"30","c4":"40"},{"id":"name2","c1":"20","c2":"40","c3":"25","c4":"38"}];

const result = _.omit(_.mergeWith({}, ...data, (objValue = 0, srcValue = 0) => +objValue + +srcValue), 'id');

console.log(result);

 console.log(_.map(result, (v, k) => ({ [k]: v }))); // or as a series of objects

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"&gt;&lt;/script&gt;

【讨论】：

有没有办法将输出更改为以下格式 [ {"c1": 30}, {"c2": 60}, { "c3": 55}, {"c4": 78}]
你可以在结果上使用 lodash 的 _.map() -> _.map(result, (v, k) => ({ [k]: v }));。我在第二个答案中添加了一个示例。

【解决方案2】：

ES6 语法：

const a =  [
        {
    "id": "name1",
    "c1": "10",
    "c2": "20",
    "c3": "30",
    "c4": "40"
        },
    {
    "id": "name2",
    "c1": "20",
    "c2": "40",
    "c3": "25",
    "c4": "38"
        }
    ];

const b = a.reduce((a, v) => {
  Object.keys(v).filter(e => e.startsWith('c')).forEach(k => a[k] = (a[k]) ? a[k] + +v[k] : +v[k]);
  return a;  
}, {});
   
console.log(b)

【讨论】：

【解决方案3】：

var values = [{
        "id": "name1",
        "c1": "10",
        "c2": "20",
        "c3": "30",
        "c4": "40"
    },
    {
        "id": "name2",
        "c1": "20",
        "c2": "40",
        "c3": "25",
        "c4": "38"
    }
];

var results = {
    "id": "totals",
    "c1": 0,
    "c2": 0,
    "c3": 0,
    "c4": 0
}

values.forEach(function(item) {
    results.c1 += Number(item.c1);
    results.c2 += Number(item.c2);
    results.c3 += Number(item.c3);
    results.c4 += Number(item.c4);
});

console.log(JSON.stringify(results));

【讨论】：

【解决方案4】：

假设您正在寻找结果对象，而不是对象数组：

var srcObj = [{
    "id": "name1",
    "c1": "10",
    "c2": "20",
    "c3": "30",
    "c4": "40"
  },
  {
    "id": "name2",
    "c1": "20",
    "c2": "40",
    "c3": "25",
    "c4": "38"
  }
];

var destObj = {};
srcObj.map((itm) => {
  Object.keys(itm).forEach(function (key) {
    if(key == 'id'){return;}
    if(!destObj[key]){
      destObj[key] = 0;
    }
    destObj[key] += parseInt(itm[key]);
  });
});

console.log(destObj);

【讨论】：

【解决方案5】：

使用lodash试试

总和

_.sum([4, 2, 8, 6]);
// => 20

总结

var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];

_.sumBy(objects, function(o) { return o.n; });
// => 20

// The `_.property` iteratee shorthand.
_.sumBy(objects, 'n');
// => 20

【讨论】：