JS实现如何的统计一个字符串中相同的字符个数

 1          var string="start,stop,speed,start,speed,start,relocicty,start,start,start,start";
 2          var count=1;
 3          for (let index = 0; index < string.length; index++) {
 4             var a=string.indexOf("start",index);
 5              // console.log(a);
 6             if(a!=-1&&string.indexOf("start",index)!=string.indexOf("start",index-1)){
 7                  count++;
 8             }
 9          }
10          console.log(count);