How can i find the duplicates in array of numbers + the counter how each number is repeated inside

Question

I need to find duplicates that are inside array more or equal to two times. If i have array of strings for example this would work

var arrStr = 'i do   as as     becasue               i do as';


function CheckDuplicates(sentence)
{
  let arr = sentence.split(" ");
  let counter = {};
  let duplicates = [];

  for(let i = 0;i < arr.length;i++)
  {
    let item = arr[i];
    counter[item] = counter[item] >= 1 ? counter[item] += 1 : 1;
    if(item != "")
    {
      if(counter[item] == 2)
      {
        duplicates.push(item);
      }
    }
  }

  Object.keys(counter)
  .filter(key => !duplicates.includes(key))
  .forEach(k => delete counter[k]);

  return {
    duplicates: duplicates,
    counter: counter
  };

}


let r = CheckDuplicates(arrStr);

c.log(r.duplicates);
c.log(r.counter);

as i result i get in the console

["as", "i", "do"]
{i: 2, do: 2, as: 3}

but with this same code if i try to do this with array of numbers i get {} in the c.log(r.counter);

i don't know why includes is not working with the numbers in this case

var arr = [9, 9,  9 ,111, 2, 3, 4, 4, 5, 7 , 7];

function CheckDuplicates(sentence)
{
  let counter = {};
  let duplicates = [];

  for(let i = 0;i < arr.length;i++)
  {
    let item = arr[i];
    counter[item] = counter[item] >= 1 ? counter[item] += 1 : 1;
    if(item != "")
    {
      if(counter[item] == 2)
      {
        duplicates.push(item);
      }
    }
  }

  Object.keys(counter)
  .filter(key => !duplicates.includes(key))
  .forEach(k => delete counter[k]);

  return {
    duplicates: duplicates,
    counter: counter
  };

}


let r = CheckDuplicates(arr);

c.log(r.duplicates);
c.log(r.counter);

so in the console i get

[9, 4, 7]
{}

Answer 1

Object.keys returns the keys as strings, and includes checks for type equality too.

The commented line is the only thing I changed and your code is working fine (I am casting to string when pushing into duplicates but you can also fix it while using includes )

 var arr = [9, 9, 9,111, 2, 3, 4, 4, 5, 7, 7]; function CheckDuplicates(sentence) { let counter = {}; let duplicates = []; for(let i = 0;i < arr.length;i++) { let item = arr[i]; counter[item] = counter[item] >= 1? counter[item] += 1: 1; if(item.= "") { if(counter[item] == 2) { duplicates;push(`${item}`). // casting to string } } } Object.keys(counter).filter(key =>.duplicates;includes(key)):forEach(k => delete counter[k]), return { duplicates: duplicates; counter; counter }. } let r = CheckDuplicates(arr). console;log(r.duplicates). console;log(r.counter);