Aggregate array of object to single distinct value of object javascript

Question

I want to aggregate array of object into single object with each object having distinct value. But My code is not giving me desired output. Can someone please help me?

My Input : 
    [{
        "obj1" : "value1",
        "obj2" : ["abc", "def"],
        "obj3" : ["ghi"],
        "obj4" : "value4",
    },
    {
        "obj1" : "value2",
        "obj2" : ["abc", "mno"],
        "obj3" : ["klm"],
        "obj4" : "value4",
    }]


Output I want:
{
    "obj1" : ["value1","value2"]
    "obj2" : ["abc", "def","mno"],
    "obj3" : ["ghi","klm"],
    "obj4" : ["value4"]
}

My Code:
const result = filterData.reduce((a,c) => 
  (Object.keys(c).map(k => a[k] = [...a[k] || [], c[k]]), a), {})

Hassan Imam · Accepted Answer · 2021-03-10 10:15:30Z

4

You can create a single object from an array of objects using array#reduce. You can get distinct value using Set.

const data = [{ "obj1" : "value1", "obj2" : ["abc", "def"], "obj3" : ["ghi"], "obj4" : "value4", }, { "obj1" : "value2", "obj2" : ["abc", "mno"], "obj3" : ["klm"], "obj4" : "value4", }],
      result = data.reduce((r,o) => {
        Object.keys(o).forEach(k => {
          r[k] = [...new Set((r[k] || []).concat(o[k]))];
        });
        return r;
      },{});
console.log(result);

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

edited Mar 10, 2021 at 10:15

answered Mar 10, 2021 at 8:02

Hassan Imam

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3 Comments

Richard Rublev Over a year ago

Why do we need r[k] = r[k] || []; line? To check if the key exists?

Hassan Imam Over a year ago

It was initializing the array for the new key and the old key, it was not doing anything. I have updated the code

Richard Rublev Over a year ago

Great,it is much easier now to understand.

Nghi Nguyen · Accepted Answer · 2021-03-10 07:59:03Z

Here I use some helpers from lodash to solve your problem.

const input = [{
        "obj1" : "value1",
        "obj2" : ["abc", "def"],
        "obj3" : ["ghi"],
        "obj4" : "value4",
    },
    {
        "obj1" : "value2",
        "obj2" : ["abc", "mno"],
        "obj3" : ["klm"],
        "obj4" : "value4",
    }]
    
function customizer(objValue, srcValue) {
  if (_.isArray(objValue)) {
    return _.union(objValue, srcValue);
  }
}
    
const output = input.reduce((acc, cur) => {
  const modifiedCur = _.mapValues(cur, function(o) { return typeof o === 'string' ? [o]: o; }); 
  acc = _.mergeWith(acc, modifiedCur, customizer);
  return acc
},{})    
    
console.log(output)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js"></script>

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