CODEWITHSUNDEEP
javascriptlodash
Atashi Khatua
Atashi Khatua

Reputation: 3

Manipulation of array of objects in javascript using lodash or underscore.js

I have an array of object in this format:

data= [ { 'a': [{"_id":"aa","type":"credit","amount":500}]},
        { 'b': [{"_id":"ba","type":"credit","amount":600},
                {"_id":"bb","type":"refund","amount":200}]},
        { 'a': [{"_id":"aaa","type":"credit","amount":600},
                {"_id":"aab","type":"credit","amount":200}]}]

All i want to do is to achieve an object like this:

result=[ { 'a': 500 },{ 'b': 600},{ 'a': 800} ]

This basically adds up the amount field from the objects which does not have a type refund.

I have tried something with _.reject and _.sumBy of lodash but failed to get the desired output.

Upvotes: 0

Views: 759

Answers (2)

stasovlas
stasovlas

Reputation: 7406

Something like: 

const data = [{'a':[{"_id":"aa","type":"credit","amount":500}]},{'b':[{"_id":"ba","type":"credit","amount":600},{"_id":"bb","type":"refund","amount":200}]}]

const sum = (items) => _.chain(items)
  .reject({ type: 'refund' })
  .sumBy('amount')
  .value();

const res = _.map(data, item => _.mapValues(item, sum));

console.log(res)
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

Upvotes: 2

Andrew Bone
Andrew Bone

Reputation: 7291

Are you opposed to using standard javascript?

In this example, I use map to iterate through each part of the array and reduce to sum the amounts.

const objs = [{'a':[{"_id":"aa","type":"credit","amount":500}]},{'b':[{"_id":"ba","type":"credit","amount":600},{"_id":"bb","type":"refund","amount":200}]}]

let newObjs = objs.map((o) => {
  let key = Object.keys(o)[0];
  let amount = o[key].length > 1 ? o[key].reduce((a, b) => {
      return {
        amount: a.amount + (b.type == "refund" ? 0 : b.amount)
      }
    }).amount :
    o[key][0].type == "refund" ? 0 : o[key][0].amount;
  return JSON.parse(`{"${key}":${amount}}`)
})

console.log(newObjs)

The map() method creates a new array with the results of calling a provided function on every element in the calling array.

The reduce() method applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

Upvotes: 1

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