added basic-prefix-sum code

Author: rishima17

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

@@ -0,0 +1,20 @@
+import { describe, it, expect } from "vitest";
+import { basicPrefixSum } from "../BasicPrefixSum.js";
+
+describe("basicPrefixSum", () => {
+  it("computes prefix sums correctly", () => {
+    expect(basicPrefixSum([1, 2, 3, 4])).toEqual([1, 3, 6, 10]);
+  });
+
+  it("returns an empty array for empty input", () => {
+    expect(basicPrefixSum([])).toEqual([]);
+  });
+
+  it("throws an error if input is not an array", () => {
+    expect(() => basicPrefixSum("abc")).toThrow(TypeError);
+  });
+
+  it("throws an error if array contains non-numeric elements", () => {
+    expect(() => basicPrefixSum([1, "2", 3])).toThrow(TypeError);
+  });
+});