麻烦大神帮忙改下代码，找不出是哪的问题

我的代码

const Interpreter = function() {
  return {
    read:function(input){
      let stack=[0,0,0],i=0,opt=[],loop=0;
      for(var j=0;j<input.length;j++){
          switch (input.charAt(j)) {
              case '*':
                  stack[i]=0;
                  break;
              case '+':
                  stack[i]+=1;
                  break;
              case '-':
                  stack[i]-=1;
                  break;
              case '<':
                    i<1?(stack[2]=stack[0],stack[0]=0):(stack[i-1]=stack[i],stack[i]=0);
                  break;
              case '>':
                  i>1?(stack[0]=stack[2],stack[2]=0):(stack[i+1]=stack[i],stack[i]=0);
                  break;
              case '^':
                  stack[i]=0;
                  break;
              case '.':
                  opt.push(stack[i]);
                  break;
              case '#':
                  i<2?i++:i=0;
                  break;
              case ',':
                  var reg = /,\d+/;
                      reg.lastIndex=j;
                  var result = reg.exec(input);
                      if (result){
                        var lth = result[0].length-1;
                        j+=lth;
                        stack[i] = Number(result[0].slice(1));
                      }
                  break;
              case '[':
                var reg = /\[.+\]/;
                reg.lastIndex=j;
                var result = reg.exec(input);
                loop = result[0].length;
                if (stack[i]<0){
                  j+=loop;
                }
                break;
              case ']':
                if (stack[i]>0){
                  j=j-loop+1;
                }
                break;
              default:
                return false;

          }
      }
      return opt.join("");

    }
  };
}

提交结果