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.

Answer 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; } 

Answer 2

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

Answer 3

 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); 

Answer 4

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. 

Answer 5

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