Duplicate count(codewars.com)

by Alexey Zakharov

JavaScript

function duplicateCount(text){
  text = text.toLowerCase();
	var count = 0;
  var obj = {};
  Array.prototype.slice.call(text).forEach(function(item) {
  	if(item in obj) {
			obj[item] = +1;
    } else {
    obj[item] = 0;
    }
  });
	for( var i in obj) {
	  if(obj[i] > 0) count++;
  }
  return count;
}