Added insertion sort algorithm in Javascript

JavaScript/algorithms/sorting/insertion_sort.js

@@ -0,0 +1,69 @@
+/* Insertion Sort
+
+Description:
+Insertion Sort builds the final sorted array one element at a time.
+It iterates through the array, taking the current element and inserting it into its correct
+position among the already sorted elements to its left.
+
+Time Complexity: 
+- Best Case: O(n) - Already sorted array
+- Average Case: O(n²)
+- Worst Case: O(n²)
+
+Space Complexity: O(1) - In-place Algorithm
+*/
+
+
+function insertionSort(arr){
+    const n=arr.length;
+
+    for(let i=1;i<n;i++){
+        let j=i;
+
+        //shift elements greater than arr[j] one position ahead
+        while(j>0 && arr[j-1]>arr[j]){
+            //swap using destructuring
+            [arr[j-1], arr[j]]=[arr[j], arr[j-1]];
+            j--;
+        }
+    }
+
+    return arr;
+}
+
+function runTests(){
+    console.log("Insertion Sort Test cases:");
+
+    //Test 1: Regular unsorted array
+    const test1=[64, 34, 25, 12, 22, 11, 90];
+    console.log("\nTest 1 - Original: ", test1);
+    console.log("Test 1 - Sorted: ", insertionSort(test1));
+
+    //Test2: Already sorted array
+    const test2=[1, 2, 3, 4, 5];
+    console.log("\nTest 2 - Original: ", test2);
+    console.log("Test 2 - Sorted", insertionSort(test2));
+
+    //Test 3: Reverse sorted array
+    const test3=[5, 4, 3, 2, 1];
+    console.log("\nTest 3 - Original: ", test3);
+    console.log("Test 3 - Sorted: ", insertionSort(test3));
+
+    //Test 4: Array with duplicates
+    const test4=[3, 1, 4, 1, 5, 9, 2, 6, 5];
+    console.log("\nTest4 - Original: ", test4);
+    console.log("Test 4 - Sorted: ", insertionSort(test4));
+
+    //Test 5: Single element array
+    const test5=[27];
+    console.log("\nTest 5 - Original: ", test5);
+    console.log("Test 5 - Sorted: ", insertionSort(test5));
+
+    //Test 6: Empty array
+    const test6=[];
+    console.log("\nTest 6 - Original: ", test6);
+    console.log("Test 6 - Sorted: ", insertionSort(test6));
+
+}
+
+runTests();