Count_Element_In_Array.js

function countElement(array, i, acc){
  if(!i)
    i = 0;
  if(!acc)
    acc = {};
  if(array.length<=i)
    return acc;
  if(!acc[array[i]])
    acc[array[i]] = 0;
  acc[array[i]]++;
  return countElement(array, i+1, acc)
}

countElement([1,1,2,2,2,3,4,5,5,6]);

===output===
{ '1': 2, '2': 3, '3': 1, '4': 1, '5': 2, '6': 1 }