javascript获取字符串中出现次数最多的字母，并统计其出现次数

代码如下：

function checkMax(arr){
    var result = [],hash ={};
    for (var i = 0; i < arr.length; i++) {
        if (!hash[arr.charAt(i)]) {
            hash[arr.charAt(i)] = 1;
        }else{
            hash[arr.charAt(i)]++;
        }
    }
    var key = '',
    value = 0;
    for(var i in hash){
        if (hash[i]>value) {
            value = hash[i];
            key = i;
        }
    }
    return 'Maximum num of the ele is------'+key+"-------And it's value is----- "+value;
  }
  var a = 'dajldkjalsdjalsdjassldahf';
  alert(checkMax(a));