方法一：利用js的split和join方法

1 function foo(str){ 2     var max = 0; 3     var char = []; // 存放出现次数最多的字符 4     while(str){ 5         var head = str.charAt(0); 6         var arr = str.split(head); 7         var num = str.length - arr.join('').length; 8         if(num > max){ 9             max = num;10             char.length = 0;11             char.push(head);12         }else if(num === max){13             char.push(head);14         }15         str = arr.join('');16     }17     return {maxNum:max,chars:char};18 19 }

方法二：此处要用对象key查找而不是用下标遍历，前者时间是1后者是n

1 function foo(str){ 2     let result = []; 3     for(let i = 0; i < str.length; i++){ 4         if(result[str[i]]){ 5             result[str[i]] += 1; 6         }else{ 7             result.push(str[i]); 8             result[str[i]] = 1; 9         }10     }11 12     let max = 0;13     let char = [];14     for(let key in result){15         if(result[key] > max){16             char.length = 0;17             max = result[key];18             char.push(key);19         }else if(result[key] === max){20             char.push(key);21         }22     }23 24     retrun {maxNum:max,chars:char};25 26 }