function returnFirstRepeatChar2(str){

   return ((str = str.split(' ').map(function(word){

     var letters = word.split('').reduce(function(map, letter){

       map[letter] = map.hasOwnProperty(letter) ? map[letter] + 1 : 1;

       return map;

     }, {}); // map of letter to number of occurrence in the word.

     return {

       word: word,

       count: Object.keys(letters).filter(function(letter){

         return letters[letter] > 1;

       }).length // number of repeated letters

     };

   }).sort(function(a, b){

     return b.count - a.count;

   }).shift()) && str.count && str.word) || -1; //return first word with maximum repeated letters or -1

}

console.log(returnFirstRepeatChar2("Hello and hello again"));

​

​

​

​

​