How to get the duplicates objects in an array?

Question

I have an array like this:

    var clients=[{"id":1,"name":"john","age":20},
{"id":3,"name":"dean","age":23},
{"id":12,"name":"harry","age":14},
{"id":1,"name":"sam","age":22},
{"id":13,"name":"Bolivia","age":16},
{"id":7,"name":"sabi","age":60},
{"id":7,"name":"sahra","age":40},
{"id":4,"name":"natie","age":53},{"id":7,"name":"many","age":22}]

I want to find the duplicate objects and cluster them like this:

 [
       {
       "id":1,
        "clients":[
                    {"id":1,"name":"john","age":20},
                    {"id":1,"name":"sam","age":22}
                   ]
       },
     {
       "id":7,
       "clients":[
                   {"id":7,"name":"sabi","age":60},
                   {"id":7,"name":"sahra","age":40},
                   {"id":7,"name":"many","age":22}
                  ]
      }
    ]

can I do that with filter() like this:clients.reduce(//code hier)?

Research the reduce method and think about what you could do with aggregated values that aren't just sums and such, but other arrays or objects... — CherryDT
– CherryDT, Commented Dec 19, 2021 at 11:37

Tushar Shahi · Accepted Answer · 2021-12-19 12:08:57Z

2

reduce() is tailor made for this. When you want to aggregate over an array and get a computed result, you should use reduce().

find() is another array method, which helps in finding an array element based on a condition (here the matching of id property).

var clients=[{"id":1,"name":"john","age":20},
{"id":3,"name":"dean","age":23},
{"id":12,"name":"harry","age":14},
{"id":1,"name":"sam","age":22},
{"id":13,"name":"Bolivia","age":16},
{"id":7,"name":"sabi","age":60},
{"id":7,"name":"sahra","age":40},
{"id":4,"name":"natie","age":53},{"id":7,"name":"many","age":22}]


let ans = clients.reduce((agg,x,index) => {
 let findI = agg.find( a => 
  a.id === x.id
 );
 if(findI) findI.clients.push(x);
 else {
   agg.push({
     id : x.id,
     clients : [x] 
   });
 }
 return agg;
},[]);

console.log(ans);

answered Dec 19, 2021 at 12:08

Tushar Shahi

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1 Comment

Szaman Over a year ago

this might do the job but i find it extremely unreadable. good luck to the poor developer who inherits this code and tries to figure out what it does (which is likely going to be the OP in 6 months).

Deepak · Accepted Answer · 2021-12-19 11:45:24Z

The simplest solution would be to loop over the clients and check for an existing object with the same id. If yes, push to clients array. Or else, just create one.

var clients = [{ "id": 1, "name": "john", "age": 20 },
{ "id": 3, "name": "dean", "age": 23 },
{ "id": 12, "name": "harry", "age": 14 },
{ "id": 1, "name": "sam", "age": 22 },
{ "id": 13, "name": "olivia", "age": 16 },
{ "id": 7, "name": "sabi", "age": 60 },
{ "id": 7, "name": "sahra", "age": 40 },
{ "id": 4, "name": "natie", "age": 53 }, { "id": 7, "name": "kany", "age": 22 }]

const groups = [];

for (let client of clients) {
  const existingGroup = groups.find(group => group.id == client.id)
  if (existingGroup)
    existingGroup.clients.push(client);
  else {
    groups.push({ id: client.id, clients: [client] });
  }
}

console.log(groups);

You can reassign the original object with the temporary object just used for this, and continue with your business logic, which I believe is the one you are looking for.

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