How to return duplicate count of objects from an array in JavaScript ES5

Question

I am using the below code to get the count of duplicate objects that are in an array.

I am querying through a table which has groups and it's complexity. I am passing the groups and its complexities to an object. I have duplicate entries like

[
    {group: A, complexity: Simple},
    {group: A, complexity: Complex},
    {group: A, complexity: Simple},
    {group: B, complexity: Simple},
    {group: A, complexity: Medium}
]

I need the count of duplicates like below

[
    {group: A, complexity: Simple}: 2,
    {group: A, complexity: Complex}: 1,
    {group: B, complexity: Simple}: 1,
    {group: C, complexity: Medium}: 1
]

var data = {};
var app = [];

for(let i=0; i<=2; i++){
  var fName = "Ram";
  var lName = "Krishna";
data = { "ID": fName, "Status": lName };
app.push(data);
}

var call = JSON.stringify(duplicate(app));
console.log("call: " + call);


function duplicate(app)
{
var counts = {};

for(var i =0; i < app.length; i++)
{
 
  var ab = JSON.stringify(app[i]);
    if (counts[ab])
    {
       counts[ab] += 1;
    }else{
       counts[ab] = 1;
    }
} 
return counts;

}

I am getting the below output

call: {"{\"ID\":\"Ram\",\"Status\":\"Krishna\"}":3}

What I am expecting

call: {"{"ID":"Ram","Status":"Krishna"}":3}

Can anyone please help me with this?

Why do you want to stringify? What happens when you do not stringify and log? — Tushar Shahi
– Tushar Shahi, Commented Jun 24, 2021 at 18:40
alot of bad practices here don't stringify object to make it key you need to be clear with what do you want. why on earth you want object to be key in your count object. — Toufiq Ahmed
– Toufiq Ahmed, Commented Jun 24, 2021 at 18:53
Inorder to help to your question we need more information as clearly — Mohamed Raza
– Mohamed Raza, Commented Jun 24, 2021 at 18:59

Jaspreet Singh · Accepted Answer · 2021-06-24 19:05:51Z

1

Use the below method, further improvements possible:

const getDuplicates = arr => { 
  const dupCount = arr.reduce((acc, curr) => {
    acc[curr] = acc[curr] ? acc[curr] + 1 : 1;
    return acc;
  }, {});
  return Object.entries(dupCount).filter(([k, v]) => v > 1).map(([k, v]) => k)
}

answered Jun 24, 2021 at 19:05

Jaspreet Singh

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