Creating a new array of objects from an existing object based no duplication

Question

I don't think what I want is anything special, I just cant get my head round how to do it. I have an array of objects -

{   
    "year": 2016,
    "some stuff": "bla0",
    "other stuff": 20
},
    "year": 2017,
    "some stuff": "bla1",
    "other stuff": 21
},
    "year": 2016,
    "some stuff": "bla2",
    "other stuff": 22
}

I want to create the following array of objects from the above.

{
    "2016": [
        {
            "year": 2016,
            "some stuff": "bla0",
            "other stuff": 20
        },
        {
            "year": 2016,
            "some stuff": "bla2",
            "other stuff": 22
        }
    ],
    "2017": [
        {
            "year": 2017,
            "some stuff": "bla1",
            "other stuff": 21
        }
    ]
}

My current WIP code is on https://codepen.io/sharperwebdev/pen/aqQQZy/?editors=1011 pertinent JS lines start at 167. Any help with getting my thinking straight on this would be appreciated.

Probably create a new object, then use array forEach to iterate over each item in the array and check the year-- then see if that year exists as a property in your new object yet. If not, create an property for the year, assigned an array as a value. Then, push the current object in your forEach to the array at that property in the new object. Also, incidentally, it is sort of frowned upon to link out to a whole project. Read minimal reproducible example. — Alexander Nied
– Alexander Nied, Commented Mar 1, 2018 at 15:31

Ele · Accepted Answer · 2018-03-01 15:33:21Z

1

Use the function reduce

var array = [{    "year": 2016,    "some stuff": "bla0",    "other stuff": 20  },  {    "year": 2017,    "some stuff": "bla1",    "other stuff": 21  },  {    "year": 2016,    "some stuff": "bla2",    "other stuff": 22  }]

var result = array.reduce((a, c) => {
  if (a[c.year]) a[c.year].push(c);
  else a[c.year] = [c];
  return a;
}, {});
console.log(result);

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

answered Mar 1, 2018 at 15:33

Ele

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1 Comment

Sharper Over a year ago

Perfect! thanks Ele. This is exactly what I was looking for. The others were good also which is why I've up voted the correctly working solutions.

Vic · Accepted Answer · 2018-03-01 15:33:28Z

1

You want to group your array of objects by the year? You can do something like:

const data = [{   
  "year": 2016,
  "some stuff": "bla0",
  "other stuff": 20
}, {
  "year": 2017,
  "some stuff": "bla1",
  "other stuff": 21
}, {
  "year": 2016,
  "some stuff": "bla2",
  "other stuff": 22
}];

function groupBy(data, key) {
  return data.reduce((result, item) => {
    result[item[key]] = result[item[key]] || [];
    result[item[key]].push(item);
    return result;
  }, {});
}

groupBy(data, 'year');

jsbin demo: http://jsbin.com/jifozivuve/edit?js,console

answered Mar 1, 2018 at 15:33

Vic

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Comments

LellisMoon · Accepted Answer · 2018-03-01 15:35:22Z

1

var objArray=[{   
    "year": 2016,
    "some stuff": "bla0",
    "other stuff": 20
},{
    "year": 2017,
    "some stuff": "bla1",
    "other stuff": 21
},{
    "year": 2016,
    "some stuff": "bla2",
    "other stuff": 22
}];
var newObjArray={};

objArray.forEach(function(item){
var year=item.year;
  if(!newObjArray.hasOwnProperty(year)){
    newObjArray[year]=[item];
  }else{
    newObjArray[year].push(item);
  }
});
console.log(newObjArray);

answered Mar 1, 2018 at 15:35

LellisMoon

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Comments

brk · Accepted Answer · 2018-03-01 15:35:29Z

1

You can loop the existing array using forEach and add year as akey to a new object.

var oldArr = [{
  "year": 2016,
  "some stuff": "bla0",
  "other stuff": 20
}, {
  "year": 2017,
  "some stuff": "bla1",
  "other stuff": 21
}, {
  "year": 2016,
  "some stuff": "bla2",
  "other stuff": 22
}]

var newObj = {};
oldArr.forEach(function(item) {
  if (newObj.hasOwnProperty(item.year)) {
    newObj[item.year].push(item)
  } else {
    newObj[item.year] = [];
    newObj[item.year].push(item)
  }
});
console.log(newObj)

I want to create the following array of objects from the above.

answered Mar 1, 2018 at 15:35

brk

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Comments

Naga Sai A · Accepted Answer · 2018-03-01 15:49:16Z

1

To achieve expected result, use below option of using map

var x = [{   
    "year": 2016,
    "some stuff": "bla0",
    "other stuff": 20
},{
    "year": 2017,
    "some stuff": "bla1",
    "other stuff": 21
},{
    "year": 2016,
    "some stuff": "bla2",
    "other stuff": 22
}]

var y =[]
x.map(function(e){
  var temp ={}
  temp[e.year] = e
  y.push(temp)
})

console.log(y)

https://codepen.io/nagasai/pen/yvZdQY

answered Mar 1, 2018 at 15:49

Naga Sai A

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