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);