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

Question

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.

stasovlas · Accepted Answer · 2018-07-23 12:35:33Z

2

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>

edited Jul 23, 2018 at 12:35

answered Jul 23, 2018 at 12:01

stasovlas

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2 Comments

Gruff Bunny Over a year ago

Beautiful, clean answer

Aramil Rey Over a year ago

It is not okay to add another question after your original question was solved, if this answer solved your question, please mark it as the correct solution.

Andrew Bone · Accepted Answer · 2018-07-23 12:33:23Z

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.

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