count duplicate elements in array js

1var array = [1, 2, 2, 3, 3, 4, 5, 6, 2, 3, 7, 8, 5, 22, 1, 2, 511, 12, 50, 22];
2
3console.log([...new Set(
4  array.filter((value, index, self) => self.indexOf(value) !== index))]
5);

1arr.reduce((b,c)=>((b[b.findIndex(d=>d.el===c)]||b[b.push({el:c,count:0})-1]).count++,b),[]);

1const findDuplicates = (nums) => {
2  nums.sort(); // alters original array
3  let ans = []
4
5  for(let i = 0; i< nums.length; i++){
6    if(nums[i] === nums[i+1]){
7       if(ans[ans.length -1] !== nums[i]){
8          ans.push(nums[i])
9       }
10    } 
11  }
12  return ans;
13}
14