JavaScript Binary Search Implementation
Here’s a concise explanation of binary search in JavaScript, along with an example implementation.
What is Binary Search?
Binary search is an efficient algorithm for finding a target value within a sorted array. It works by repeatedly dividing the search interval in half. If the target value is less than the middle element, it searches the left half; if it’s greater, it searches the right half. This process continues until the target value is found or the interval is empty.
Binary Search Algorithm Steps
- Initialize two pointers,
left
andright
, to the start and end of the array. - Calculate the
mid
index as the average ofleft
andright
. - Compare the middle element with the target:
- If they are equal, return the mid index.
- If the target is less than the middle element, move the right pointer to mid - 1.
- If the target is greater, move the left pointer to mid + 1.
- Repeat steps 2-3 until the target is found or the pointers cross.
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function binarySearch(arr, target) {
let left = 0;
let right = arr.length - 1;
while (left <= right) {
const mid = Math.floor((left + right) / 2);
if (arr[mid] === target) {
return mid; // Target found
}
if (arr[mid] < target) {
left = mid + 1; // Search right half
} else {
right = mid - 1; // Search left half
}
}
return -1; // Target not found
}
// Example usage:
const sortedArray = [1, 3, 5, 7, 9, 11, 13];
const target = 7;
const result = binarySearch(sortedArray, target);
console.log(result); // Output: 3 (index of the target)
This implementation provides a time complexity of $𝑂(log 𝑛)$, making it much more efficient than a linear search for large datasets.