Javascript Array find most common word

var mostCommonWord = function(arr){
   var obj = {},/*from   ww w  .j a v  a  2s.  co m*/
       placeHolder,
       max = 0;

   for(var i = 0; i < arr.length; i++){
      if(obj[arr[i]] === undefined){
        obj[arr[i]] = 1;
      }else{
        obj[arr[i]]++;
      }

      if(obj[arr[i]] > max){
       max = obj[arr[i]];
         placeHolder = arr[i];
      }
   }
   return [placeHolder, max];
};

console.log(mostCommonWord(['pear', 'apple', 'orange', 'pear','apple', 'pear']));
console.log(mostCommonWord(['pen', 'book', 'appl', 'ipad', 'pen', 'book']));