Add binarySearech

snippets/binarySearch.md

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+---
+title: binarySearch
+tags: algorithm,array,beginner
+---
+
+Finds the index of a given element in a sorted array using the binary search algorithm.
+
+- Declare the left and right search boundaries, `l` and `r`, initialized to `0` and the `length` of the array respectively.
+- Use a `while` loop to repeatedly narrow down the search subarray, using `Math.floor()` to cut it in half.
+- Return the index of the element if found, otherwise return `-1`.
+- **Note:** Does not account for duplicate values in the array.
+
+```js
+const binarySearch = (arr, item) => {
+  let l = 0,
+    r = arr.length - 1;
+
+  while (l <= r) {
+    const mid = Math.floor((l + r) / 2);
+    const guess = arr[mid];
+    if (guess === item) return mid;
+
+    if (guess > item) r = mid - 1;
+    else l = mid + 1;
+  }
+
+  return -1;
+};
+```
+
+```js
+binarySearch([1, 2, 3, 4, 5], 1); // 0
+binarySearch([1, 2, 3, 4, 5], 5); // 4
+binarySearch([1, 2, 3, 4, 5], 6); // -1
+```