Added the new algorithm TwoSum using array in Data Structure

Data-Structures/Array/TwoSum.js

@@ -0,0 +1,20 @@
+/** 
+ * This function will accept an array and a target value,
+ * and return the indexes of the two numbers that add up to the target.
+ * If no such pair exists, it returns null.
+ * @param {number[]} nums - array of numbers
+ * @param {number} target - target sum
+ * @returns {number[] | null} - array containing two indexes or null
+ */
+
+const twoSum = (nums, target) => {
+  for (let i = 0; i < nums.length; i++) {
+    for (let j = i + 1; j < nums.length; j++) {
+      if (nums[i] + nums[j] === target) 
+        return [i, j]
+    }
+  }
+  return null
+}
+
+export { twoSum }

Data-Structures/Array/test/TwoSum.test.js

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+import { twoSum } from '../TwoSum'
+
+describe('twoSum tests', () => {
+  it('should return indices for a normal case', () => {
+    const nums = [2, 7, 11, 15]
+    const target = 9
+    expect(twoSum(nums, target)).toEqual([0, 1])
+  })
+
+  it('should return indices when pair is in middle', () => {
+    const nums = [1, 4, 6, 8, 5]
+    const target = 11
+    expect(twoSum(nums, target)).toEqual([2, 4])
+  })
+
+  it('should handle negative numbers', () => {
+    const nums = [-3, 4, 3, 90]
+    const target = 0
+    expect(twoSum(nums, target)).toEqual([0, 2])
+  })
+
+  it('should return null if no pair found', () => {
+    const nums = [1, 2, 3, 4]
+    const target = 100
+    expect(twoSum(nums, target)).toBeNull()
+  })
+
+  it('should work with duplicate numbers', () => {
+    const nums = [3, 3]
+    const target = 6
+    expect(twoSum(nums, target)).toEqual([0, 1])
+  })
+})