541. 反转字符串 II

题目链接

 function reverseStr(s: string, k: number): string {
   let sArray = [...s]; // string类型在ts下不支持修改索引
   let needTrans = true;
   for(let i=0;i < sArray.length;i+=k) {
      if(needTrans) {
         const sub = sArray.slice(i,i+k);
         for(let j = sub.length-1;j>=0;j--) {
            const id = i + sub.length - 1 - j;
            sArray[id] = sub[j];
         }
      }
      needTrans = !needTrans;
   }
   return sArray.join('');
 };