```ts
/**
 * Finds the first and last occurrence of the target in a sorted array using binary search.
 * Returns [firstIndex, lastIndex] or [-1, -1] if target is not found.
 */
export function searchRange(nums: number[], target: number): [number, number] {
  const findFirst = (): number => {
    let left = 0;
    let right = nums.length - 1;
    let result = -1;

    while (left <= right) {
      const mid = Math.floor((left + right) / 2);
      if (nums[mid] === target) {
        result = mid;
        right = mid - 1;
      } else if (nums[mid] < target) {
        left = mid + 1;
      } else {
        right = mid - 1;
      }
    }

    return result;
  };

  const findLast = (): number => {
    let left = 0;
    let right = nums.length - 1;
    let result = -1;

    while (left <= right) {
      const mid = Math.floor((left + right) / 2);
      if (nums[mid] === target) {
        result = mid;
        left = mid + 1;
      } else if (nums[mid] < target) {
        left = mid + 1;
      } else {
        right = mid - 1;
      }
    }

    return result;
  };

  const firstIndex = findFirst();
  if (firstIndex === -1) {
    return [-1, -1];
  }

  const lastIndex = findLast();
  return [firstIndex, lastIndex];
}
```