JavaScript趣题：求数组出现频率最大元素

arr = [12, 10, 8, 12, 7, 6, 4, 10, 12]; 
highestRank(arr) //=> returns 12 
 
arr = [12, 10, 8, 12, 7, 6, 4, 10, 12, 10]; 
highestRank(arr) //=> returns 12 
 
arr = [12, 10, 8, 8, 3, 3, 3, 3, 2, 4, 10, 12, 10]; 
highestRank(arr) //=> returns 3

function highestRank(arr){ 
 var hash = {}; 
 var highest = 0; 
 var highestArray = []; 
 for(var i=0;i<arr.length;i++){ 
 var cur = arr[i]; 
 if(hash[cur]){ 
 hash[cur] = 1 + hash[cur]; 
 } 
 else{ 
 hash[cur] = 1; 
 } 
 if(hash[cur] > highest){ 
 highest = hash[cur]; 
 } 
 } 
 for(var j in hash){ 
 if(hash.hasOwnProperty(j)){ 
 if(hash[j] === highest){ 
 highestArray.push(j); 
 } 
 } 
 } 
 return Math.max.apply(null,highestArray); 
}