Added binary search algo

Author: Defite

base-algorithms/binarySearch.ts

@@ -0,0 +1,24 @@
+/**
+ * Binary search algorithm
+ * Complexity: O(log(n))
+ */
+
+function binarySearch(arr: number[], item: number) {
+    let start = 0;
+    let end = arr.length - 1;
+
+    while (start <= end) {
+        let mid = Math.floor(start + end) / 2;
+        let guess = arr[mid];
+
+        if (guess === item) {
+            return true;
+        } else if (guess < item) {
+            start = mid + 1;
+        } else {
+            end = mid - 1;
+        }
+    }
+
+    return false;
+}