function findInCircularlySortedAry (ary = [], target) {  if (ary && ary.length === 0) {    return -1;  }    if (ary.length === 1) {      return ary[0] === target ? 0 : -1;  }    let low = 0,      high = ary.length - 1;    while(low <= high) {    let mid = Math.floor((low + high) / 2);    // case 1: target === middle item, return found    if (ary[mid] === target) {       return mid;    }    // To find which parts (left or right) is sorted    // case 2: if middle < high, mean from middle to high is sorted    if (ary[mid] < ary[high]) {       if (target > ary[mid] && target <= ary[high]) {           low = mid + 1;       } else {         high = mid - 1;       }    }     // case 3: if low < middle, mean from low to middle is sorted    else {      if (target >= ary[low] && target < ary[mid]) {        high = mid -1;      } else {        low = mid + 1;      }    }   }    return -1;}const data = [12,14,18,21,3,6,8,9];const res = findInCircularlySortedAry(data,18); // 2console.log(res);

We don't need to