js 统计字符串中出现次数最多的字符？

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Document</title>
 6     <script>
 7     
 8         var s="aaaabbbbssssssss";
 9             var fres={};  //用来记录所有的字符的出现频次
10             var mostFreqChar=''; //用来记录最大频次的字符
11             for(var i=0;i<s.length;i++){
12                 var char=s[i];
13                 if(!fres[char]){
14                     fres[char]=0;
15                 }
16 
17                 fres[char]++;            
18                 if(mostFreqChar==''||fres[char]>fres[mostFreqChar]){
19                     mostFreqChar=char;
20                 }
21 
22             }
23             console.log(mostFreqChar);
24             console.log(fres[mostFreqChar]);
25 
26     </script>
27 </head>
28 <body>
29     
30 </body>
31 </html>