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.

Answer 1

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> 

Answer 2

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) 

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

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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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