Merge objects in array based on property

Question

I have an array like so which i am trying to merge so any object that has the name property the same will after the merge contain a list of merged objects

var array = [ 
    {name: "One",
     myList: [Object1, Object2]
    },
    {name: "Two",
     myList: [Object3, Object4]
     },
     {name: "One",
     myList: [Object5, Object6]
     }
]

How do i merge the two 'One' objects so i get something like

var array = [ 
    {name: "One",
     myList: [Object1, Object2, Object5, Object6]
    },
    {name: "Two",
     myList: [Object3, Object4]
     }
]

looking to do this in vanilla javascript

tymeJV · Accepted Answer · 2017-04-07 15:01:13Z

3

Using reduce:

var merged = array.reduce(function(list, obj) {
    var found = false;
    for (var i = 0; i < list.length; i++) {
        if (list[i].name == obj.name) {
            list[i].myList = list[i].myList.concat(obj.myList);
            found = true;
            break;
        }
    }

    if (!found) {
        list.push(obj);
    }

    return list;
}, []);

answered Apr 7, 2017 at 15:01

tymeJV

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Comments

kind user · Accepted Answer · 2017-04-07 15:12:38Z

1

Firstly you could remove the duplicate entries and organize the objects inside the myList array. Then, return an array of objects with specified keys, based on the ordered object from the first step.

var array = [{name:"One",myList:['Object1','Object2']},{name:"Two",myList:['Object3','Object4']},{name:"One",myList:['Object5','Object6']}], obj = {};

array.forEach(function(v) {
  obj[v.name] = (obj[v.name] || []).concat(v.myList)
});

var arr = Object.keys(obj).reduce(function(s,a) {
  s.push({name: a, myList: obj[a]});
  return s;
}, []);

console.log(arr);

edited Apr 7, 2017 at 15:12

answered Apr 7, 2017 at 15:03

kind user

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4 Comments

Rajesh Dixit Over a year ago

You can try obj[v.name] = (obj[v.name] || []).concat(v.myList)

kind user Over a year ago

@Rajesh Inside the foreach?

Rajesh Dixit Over a year ago

@Kinduser Yes. spread operator is part of ES6 and is not available in all browsers

Rajesh Dixit Over a year ago

@blu10 I think everything else would work. You can replace code I suggested inside forEach and it should be good

Taro Wong · Accepted Answer · 2018-04-01 20:17:17Z

0

Another approach using Lodash with just chain and reduce

var array = [
    { name: "One", myList: ["Object1", "Object2"] },
    { name: "Two", myList: ["Object3", "Object4"] },
    { name: "One", myList: ["Object5", "Object6"] }
  ];

  const newArray = _.chain(array)
    .reduce((acc, currentValue) => {
      acc[currentValue.name] = (acc[currentValue.name] || []).concat(
        currentValue.myList
      );
      return acc;
    }, {})
    .reduce((acc, currentValue, key) => {
      acc.push({ name: key, myList: currentValue }); 
      return acc;
    }, [])
    .value();

  console.log(newArray);

answered Apr 1, 2018 at 20:17

Taro Wong

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