How to sum values of certain properties for each subgroup nested array object's in Javascript?

Question

From the object below, I wanted to sum up certain properties (fare+tax and com+agency) by their key group (1345, 2353) and updated it in the current array object.

var details = [{ 1345:[
                {route: 34, fare: 45, tax: 46, date: 46, com: 45, agency: 24, totalCost: 0, totalFee: 0}], 
               2353: [
                {route: 32, fare: 45, tax: 45, date: 56, com: 34, agency: 52, totalCost: 0, totalFee: 0}, 
                {route: 42, fare: 34, tax: 64, date: 34, com: 56, agency: 34, totalCost: 0, totalFee: 0}
              ]} 
             ]

expected output: updated details (totalCost and totalFee)

    1345: 
{ route: 34, fare: 45, .... totalCost: 91, totalFee: 69 }
    2353: 
{ route: 32, fare: 45, ... totalCost: 188, totalFee: 90 },
{ route: 42, fare: 34, ... totalCost: 188, totalFee: 176 }

totalCost = fare + tax and totalFee = com + agency

I tried to simplified the array objects and convert by using Object.entries(details[0]), then reduce to sum up the target properties.

Object.entries(details[0]).reduce((acc, curr) => (acc = acc + curr["fare"]+curr["tax"]), 0);

However, NaN was returned.

Would appreciate if anyone could show me how I can loop through each key group and sum up the target values and update it (totalCost and totalFee).

You should use Object.values instead of Object.entries, and also you don't need to assign a new value to acc. — k.tten
– k.tten, Commented Aug 30, 2022 at 14:07
Pretty sure that totalFee on 2353 is wrong (34 + 52 + 56 + 34) !== 90 — benbotto
– benbotto, Commented Aug 30, 2022 at 14:27
@kelly I tried changing Object.entries to .values and remove acc, but it still doesn't work. If possible, can you give me an example? **I have updated my question and expected output. Thanks alot! — hans1125
– hans1125, Commented Sep 5, 2022 at 10:21
@benbotto you're right! I was in a hurried and didn't realized that... — hans1125
– hans1125, Commented Sep 5, 2022 at 10:21

benbotto · Accepted Answer · 2022-09-06 14:16:40Z

2

One way (of many) would be to use a simple sum function to sum up an arbitrary array of values:

function sum(...nums) {
  return nums.reduce((acc, val) => acc + val)
}

Next, sum up the totalCost/totalFee logic for each key group (1345 and 2353), and then apply the sums to each array entry:

for (const [key, vals] of Object.entries(details[0])) {
  vals.forEach((val, _, vals) => {
    val.totalFee  = sum(...vals.map(val => val.com + val.agency))
    val.totalCost = sum(...vals.map(val => val.fare + val.tax))
  })
}

Here's the whole shebang:

const details = [
  {
    1345: [
      {route: 34, fare: 45, tax: 46, date: 46, com: 45, agency: 24, totalCost: 0, totalFee: 0},
    ], 
    2353: [
      {route: 32, fare: 45, tax: 45, date: 56, com: 34, agency: 52, totalCost: 0, totalFee: 0}, 
      {route: 42, fare: 34, tax: 64, date: 34, com: 56, agency: 34, totalCost: 0, totalFee: 0},
    ],
  },
]

for (const [key, vals] of Object.entries(details[0])) {
  vals.forEach((val, _, vals) => {
    val.totalFee  = sum(...vals.map(val => val.com + val.agency))
    val.totalCost = sum(...vals.map(val => val.fare + val.tax))
  })
}

console.log(JSON.stringify(details, null, 2))

function sum(...nums) {
  return nums.reduce((acc, val) => acc + val)
}

edited Sep 6, 2022 at 14:16

answered Aug 30, 2022 at 14:25

benbotto

2,4491 gold badge23 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

hans1125 Over a year ago

Thanks for the answer. If I just wanted to update the current array object 'details' (totalCost and totalFee) or create new object with the same properties structure as 'details' , how should I modified the function ? **Each keygroup(1345, 2353) contains multiple objects. Appreciate your help!

benbotto Over a year ago

@hans1125 I've updated the code per your comment. Now the two totals are updated in the original details object.

Terry Lennox · Accepted Answer · 2022-09-05 10:45:31Z

2

We can do this using a few Array.reduce() calls, the end result should be as required.

For each key group, we'd use Object.entries() to get the key and value for the group.

const details = [{ 1345:[ {route: 34, fare: 45, tax: 46, date: 46, com: 45, agency: 24, totalCost: 0, totalFee: 0}], 2353: [ {route: 32, fare: 45, tax: 45, date: 56, com: 34, agency: 52, totalCost: 0, totalFee: 0}, {route: 42, fare: 34, tax: 64, date: 34, com: 56, agency: 34, totalCost: 0, totalFee: 0} ]} ]
         
const result = details.reduce((acc, group) => { 
    return Object.entries(group).reduce((acc, [key, routes] ) => {
        return routes.reduce((acc, { fare, tax, com, agency}) => { 
            acc[key] = acc[key] || {};
            acc[key].totalCost = (acc[key].totalCost || 0) + fare + tax;
            acc[key].totalFee = (acc[key].totalFee || 0) + com + agency;
            return acc;
        }, acc)
    }, acc)
}, {})

console.log('Result:', result)

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

I've updated here to include the original array under each key group, naming it 'routes', this could be changed to anything:

const details = [{ 1345:[ {route: 34, fare: 45, tax: 46, date: 46, com: 45, agency: 24, totalCost: 0, totalFee: 0}], 2353: [ {route: 32, fare: 45, tax: 45, date: 56, com: 34, agency: 52, totalCost: 0, totalFee: 0}, {route: 42, fare: 34, tax: 64, date: 34, com: 56, agency: 34, totalCost: 0, totalFee: 0} ]} ]

const result = details.reduce((acc, group) => { 
    return Object.entries(group).reduce((acc, [key, routes] ) => {
        return routes.reduce((acc, { fare, tax, com, agency}) => { 
            acc[key] = acc[key] || { routes };
            acc[key].totalCost = (acc[key].totalCost || 0) + fare + tax;
            acc[key].totalFee = (acc[key].totalFee || 0) + com + agency;
            return acc;
        }, acc)
    }, acc)
}, {})

console.log('Result:', result)

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

edited Sep 5, 2022 at 10:45

answered Aug 30, 2022 at 14:29

Terry Lennox

30.9k5 gold badges36 silver badges45 bronze badges

2 Comments

hans1125 Over a year ago

Thanks you! If I just wanted to update the current array object 'details' (totalCost and totalFee) or create new object with the same properties structure as 'details', how should I modified the function ? **Each keygroup(1345, 2353) contains multiple objects. Appreciate your help!

Terry Lennox Over a year ago

I've added another snippet to include the array under each key group as 'routes'. You could call this something else of course!

Joe Moore · Accepted Answer · 2022-08-31 14:05:47Z

1

Expanding on the use of Object.values

var details = [{ 1345:[
                {route: 34, fare: 45, tax: 46, date: 46, com: 45, agency: 24, totalCost: 0, totalFee: 0}], 
               2353: [
                {route: 32, fare: 45, tax: 45, date: 56, com: 34, agency: 52, totalCost: 0, totalFee: 0}, 
                {route: 42, fare: 34, tax: 64, date: 34, com: 56, agency: 34, totalCost: 0, totalFee: 0}
              ]} 
             ]

Object.values(details).map(x => {
  details = {}
  let count = 0;
  for (let y of Object.values(x)) {
    y = y.reduce(function (a, b) {
      for (const key in b) {
        if (a[key]) {
          a[key] = a[key] + b[key]
        } else {
          a[key] = b[key];
        }
      }
      return a;
    }, {});
    y['totalCost'] = y['fare'] + y['tax']; 
    y['totalFee'] = y['com'] + y['agency'];
    let totalObj = {};
    totalObj['totalCost:'] = y['totalCost'];
    totalObj['totalFee:'] = y['totalFee'];
    details[`${Object.keys(x)[count]}`] = totalObj;
    count++;
  };
});

console.log(details);

edited Aug 31, 2022 at 14:05

answered Aug 30, 2022 at 14:32

Joe Moore

2,0232 gold badges10 silver badges35 bronze badges

2 Comments

hans1125 Over a year ago

Thanks alot! If I just wanted to update the current array object 'details' (totalCost and totalFee) or create new object with the same properties structure as 'details', how should I modified the function ? **Each keygroup(1345, 2353) contains multiple objects like in 'details'. Your help is appreciated!

Joe Moore Over a year ago

That's a difficult one because you can have multiple objects in one key group - so would you want to add totalCost and totalFee to all details elements? If so that appears a bit counterintuitive since the totalCost and totalFee will not look as if they've been summed correctly.

Collectives™ on Stack Overflow

How to sum values of certain properties for each subgroup nested array object's in Javascript?

3 Answers 3

2 Comments

2 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

2 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related