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);  
}