# Find First and Last Position of Element in Sorted Array in TypeScript

function searchRange(nums: number[], target: number): number[] {
// binarySearchLeft: A modified binary search function to find the leftmost index of the target.
function binarySearchLeft(nums: number[], target: number): number {
let left: number = 0, right: number = nums.length - 1;
while (left <= right) {
// Calculate the middle index of the current search range.
let mid: number = left + Math.floor((right - left) / 2);

// Narrow down the search to the left half if the target is less than or equal to the middle element.
if (nums[mid] < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
// Return the left boundary which points to the first occurrence of the target.
return left;
}

// binarySearchRight: A modified binary search function to find the rightmost index of the target.
function binarySearchRight(nums: number[], target: number): number {
let left: number = 0, right: number = nums.length - 1;
while (left <= right) {
// Calculate the middle index of the current search range.
let mid: number = left + Math.floor((right - left) / 2);

// Narrow down the search to the right half if the target is greater than the middle element.
if (nums[mid] <= target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
// Return the right boundary which points to the last occurrence of the target.
return right;
}

// Use the binary search functions to find the first and last positions of the target.
let first: number = binarySearchLeft(nums, target);
let last: number = binarySearchRight(nums, target);

// Check if the target is present in the array.
// If first is less than or equal to last, the target is present, and we return the indices.
// Otherwise, return [-1, -1] indicating the target is not present.
if (first <= last) {
return [first, last];
}
return [-1, -1];
}