From 1cca9867e3a34cd32c95fe28f801bff934efd816 Mon Sep 17 00:00:00 2001
From: Suhas-30 <3suhashs@gmail.com>
Date: Wed, 30 Jul 2025 20:06:53 +0530
Subject: [PATCH] feat: add BasicPrefixSum algorithm and tests

---
 PrefixSum/BasicPrefixSum.js            | 18 ++++++++++++++++++
 PrefixSum/tests/BasicPrefixSum.test.js | 21 +++++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 PrefixSum/BasicPrefixSum.js
 create mode 100644 PrefixSum/tests/BasicPrefixSum.test.js

diff --git a/PrefixSum/BasicPrefixSum.js b/PrefixSum/BasicPrefixSum.js
new file mode 100644
index 0000000000..f1513bcc98
--- /dev/null
+++ b/PrefixSum/BasicPrefixSum.js
@@ -0,0 +1,18 @@
+function prefixSum(arr) {
+  if (!Array.isArray(arr) || arr.some((num) => typeof num !== 'number')) {
+    throw new TypeError(`Input must be an array of numbers`)
+  }
+
+  const pSum = []
+
+  let sum = 0
+
+  for (const num of arr) {
+    sum += num
+    pSum.push(sum)
+  }
+
+  return pSum
+}
+
+export { prefixSum }
diff --git a/PrefixSum/tests/BasicPrefixSum.test.js b/PrefixSum/tests/BasicPrefixSum.test.js
new file mode 100644
index 0000000000..29d0d9bd5d
--- /dev/null
+++ b/PrefixSum/tests/BasicPrefixSum.test.js
@@ -0,0 +1,21 @@
+import { prefixSum } from '../BasicPrefixSum.js'
+import { describe, it, expect } from 'vitest'
+
+describe('prefixSum', () => {
+  it(`Should return computed prefix sum array for a passed input array`, () => {
+    expect(prefixSum([3, 6, 9, 15])).toEqual([3, 9, 18, 33])
+    expect(prefixSum([0, 5, -2, 4])).toEqual([0, 5, 3, 7])
+  })
+
+  it(`Should return empty array when passed input array is empty`, () => {
+    expect(prefixSum([])).toEqual([])
+  })
+
+  it(`should throw TypeError if input is not an array of numbers`, () => {
+    expect(() => prefixSum('array')).toThrow(TypeError)
+    expect(() => prefixSum(1)).toThrow(TypeError)
+    expect(() => prefixSum([1, '2'])).toThrow(TypeError)
+    expect(() => prefixSum([1, true])).toThrow(TypeError)
+    expect(() => prefixSum([{}, 2])).toThrow(TypeError)
+  })
+})