feat: add BasicPrefixSum algorithm and tests

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 }

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)
+  })
+})