Creating a SUM of nested object values in JavaScript

Question

I'm using the following code to query an API, which is working well to return nested values in JSON:

const obj = response.data.map(function(item) {

return [item.id, item.jobNumber];
});

Example JSON:

{
 "data": [
  {
     "id": 100,
     "jobNumber": 1,
     "jobTasks": [
        {
           "id": 12,
           "cost": {
              "amountString": 100
           },
           {
           "id": 13,
           "cost": {
              "amountString": 500
           }
         }
     }
  ]
},
  {
     "id": 101,
     "jobNumber": 2,
     "jobTasks": [
        {
           "id": 14,
           "cost": {
              "amountString": 100
           },
          {
           "id": 15,
           "cost": {
              "amountString": 200
           }
         }
     }]

}]
}

I'm wanting to now loop through the nested Job Tasks, and SUM the item.jobTasks.cost.amountString for each job, So that the following could be returned:

JobNumber1: Task Costs: 600
JobNumber2: Task Costs: 300

Mihai Alexandru-Ionut · Accepted Answer · 2017-05-03 06:58:27Z

You can use reduce method which accepts a callback method.

Also, use forEach method in order to iterate data items.

var json={
 "data": [
  {
     "id": 100,
     "jobNumber": 1,
     "jobTasks": [
           {
           "id": 12,
           "cost": {
              "amountString": 100
            }
           },
           {
           "id": 13,
           "cost": {
              "amountString": 500
            }
           }
      ]
  },
  {
     "id": 101,
     "jobNumber": 2,
     "jobTasks": [
          {
           "id": 14,
           "cost": {
              "amountString": 100
           }
           },
          {
           "id": 15,
           "cost": {
              "amountString": 200
           }
          }
    ]

}]
}
json.data.forEach(function(item){
  var sum=item.jobTasks.reduce(function(sum,elem){
     return sum+elem.cost.amountString;
  },0);
   console.log('jobNumber'+item.jobNumber+' '+sum);
});

Weedoze · Accepted Answer · 2017-05-03 06:57:08Z

3

You can do it using Array#map() to create a new array and Array#reduce() to sum the amountString

const apiJson = {"data":[{"id":100,"jobNumber":1,"jobTasks":[{"id":12,"cost":{"amountString":100}},{"id":13,"cost":{"amountString":500}}]},{"id":101,"jobNumber":2,"jobTasks":[{"id":14,"cost":{"amountString":100}},{"id":15,"cost":{"amountString":200}}]}]};

const output = apiJson.data.map(d=>({
  jobNumber : d.jobNumber,
  tasksCost : d.jobTasks.reduce((a,b)=>a.cost.amountString+b.cost.amountString)
}));

console.log(output);

answered May 3, 2017 at 6:57

Weedoze

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Comments

Himanshu Shekhar · Accepted Answer · 2017-05-03 07:03:19Z

1

first Update your json , "}" is missing from jobTasks of second object of array data :

   "jobTasks": [    { "id": 14,
                    "cost": {
                         "amountString": 100 
                           }
                     },
                     {
                      "id": 15,
                  "cost": {
                        "amountString": 200
                          }
                       }
                ]

Now To get Output:

i = 0,1

item.jobTasks[i]cost.amountString;

answered May 3, 2017 at 7:03

Himanshu Shekhar

1,2601 gold badge17 silver badges42 bronze badges

Comments

vincent · Accepted Answer · 2021-01-14 01:04:50Z

Here is a solution using object-scan. We use it for most of our data processing now. It does take a moment to wrap your head around though as it is versatile.

// const objectScan = require('object-scan');

const getCounts = (data) => objectScan(['data[*].jobTasks[*].cost.amountString'], {
  filterFn: ({ parents, value, context }) => {
    const jobNumber = parents[3].jobNumber;
    context[jobNumber] = (context[jobNumber] || 0) + value;
  }
})(data, {});

const apiJson = { data: [{ id: 100, jobNumber: 1, jobTasks: [{ id: 12, cost: { amountString: 100 } }, { id: 13, cost: { amountString: 500 } }] }, { id: 101, jobNumber: 2, jobTasks: [{ id: 14, cost: { amountString: 100 } }, { id: 15, cost: { amountString: 200 } }] }] };

console.log(getCounts(apiJson));
// => { '1': 600, '2': 300 }

.as-console-wrapper {max-height: 100% !important; top: 0}

<script src="https://bundle.run/[email protected]"></script>

Disclaimer: I'm the author of object-scan

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