Get the word with the highest character repetition

main.js

var getReps = function(str){
  return _.chain(str.split(' '))
    .map(function(w){
      return {
        word: w, 
        reps: _.chain(w.toUpperCase().split(''))
          .groupBy(_.identity)
          .max(function(g){
            return g.length;
          })
          .value()
          .length;
      };
    })
    .max(function(w){
      return w.reps;
    })
    .value()
    .word;
}