Group array of objects in array of arrays -JS

Question

I'm trying to group an array of objects in array of arrays by 'group' key in objects.

Current array:

array =
[
    [{name:’a’,age:’4’,group:’15’},{name:’b’,age:’4’,group:’15’}, 
     {name:’c’,age:’4’,group:’15’}],
    [{name:’aa’,age:’6’,group:’12’},{name:’bb’,age:’6’,group:’12’}],
    [{name:’d’,age:’5’,group:’15’},{name:’e’,age:’5’,group:’15’}, 
     {name:’f’,age:’5’,group:’15’}],
    [{name:’dd’,age:’7’,group:’12’}, 
     {name:’ee’,age:’7’,group:’12’{name:’ff’,age:’7’,group:’12’}]
]

I want to get an array looking like:

newArray=  [
        {15:[[{name:’a’,age:’4’,group:’15’},{name:’b’,age:’4’,group:’15’}, 
              {name:’c’,age:’4’,group:’15’}],[{name:’d’,age:’5’,group:’15’}, 
              {name:’e’,age:’5’,group:’15’},{name:’f’,age:’5’,group:’15’}]
        },
        {12:[[{name:’aa’,age:’6’,group:’12’},{name:’bb’,age:’6’,group:’12’}],
            [{name:’dd’,age:’7’,group:’12’},{name:’ee’,age:’7’,group:’12’}, 
             {name:’ff’,age:’7’,group:’12’}]]
        }
    ]

Thank you!

ABGR · Answer 1 · 2020-06-25T12:43:38.917

0

You can do something like this using Reduce:

array =
[
    [{name:'a',age:'4',group:'15'},
     {name:'b',age:'9',group:'15'}, 
     {name:'c',age:'6',group:'15'},
     {name:'c',age:'8',group:'15'},
     {name:'c',age:'4',group:'15'}],
    [{name:'aa',age:'6',group:'12'}]
];
const groupByAge = (acc, elem)=>{
    acc[elem.age] = acc[elem.age]?  [...acc[elem.age],elem] : [elem];
    return acc
}
var res = array.reduce((acc, elem)=>{
var key = "";
  elem.forEach(k=> {
       key  = k.group;
       acc[k.group] = acc[k.group] ?  [...acc[k.group], k] : [k];
   });
  var temp= acc[key].reduce(groupByAge, {});
  acc[key] = Object.values(temp);
  return acc
},{});

console.log([res])

edited Jun 25 '20 at 12:43

answered Jun 25 '20 at 09:04

ABGR

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Thank you, but I'm looking also to separate 'age' key – user12083483 Jun 25 '20 at 09:15
I need to group by group and age – user12083483 Jun 25 '20 at 09:26
Any Ideas how to do this? – user12083483 Jun 25 '20 at 10:02
I added input and output to question. array= input , newArray=output – user12083483 Jun 25 '20 at 10:32
the key should be the 'group' value , and the value should be array of arrays cording to age – user12083483 Jun 25 '20 at 10:42
Thanks, is there any way to get the exact same output like in question? – user12083483 Jun 25 '20 at 11:35
@ABGR he wants an array of arrays, with each array grouping together ages, like in my answer – user120242 Jun 25 '20 at 11:52
@user12083483 Ah, okay. Yes you can do so. Check the updted one. But this would be further adding to complexity. Anyway. – ABGR Jun 25 '20 at 12:33

user120242 · Accepted Answer · 2020-06-25T10:59:01.313

flat to flatten the arrays.
Create object maps to group by group and age.
Extract individual objects per key in object map, and unwrap ages objects to arrays.
ages are numbers, and ES2015 sorts integer indexes, so the order is already sorted by age.

Note: your JavaScript data object is invalid JavaScript due to use of non-standard single quote. And there are unclosed brackets in your data. Parsed as string sanitized to JSON.

res = 
Object.entries(
array.flat().reduce((res,x)=>{
  const {age, group} = x
  res[group] = res[group] || {}
  res[group][age] = res[group][age] || []
  res[group][age].push(x)
  return res
},{})
).map(([k,v])=>({[k]: Object.values(v)}))

console.log(res)

<script>
array =
JSON.parse(`[
    [{name:’a’,age:’4’,group:’15’},{name:’b’,age:’4’,group:’15’}, 
     {name:’c’,age:’4’,group:’15’}],
    [{name:’aa’,age:’6’,group:’12’},{name:’bb’,age:’6’,group:’12’}],
    [{name:’d’,age:’5’,group:’15’},{name:’e’,age:’5’,group:’15’}, 
     {name:’f’,age:’5’,group:’15’}],
    [{name:’dd’,age:’7’,group:’12’}, 
     {name:’ee’,age:’7’,group:’12’},{name:’ff’,age:’7’,group:’12’}]
]`.replace(/’/g,'"').replace(/(name|age|group)/g,'"$1"'))
</script>

If an answer helped you, click the checkmark next to it to [accept it as the solution](https://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work) — user120242, Jun 25 '20 at 13:50

Group array of objects in array of arrays -JS

2 Answers2