Basic prefix sum

Data-Structures/Array/BasicPrefixSum.js

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+/**
+ * Computes prefix sums for a numeric array.
+ * Example: [2, 3, 5] → [2, 5, 10]
+ * @param {number[]} arr
+ * @returns {number[]} Prefix sum array
+ * @throws {TypeError} if input is not a numeric array
+ */
+export const basicPrefixSum = (arr) => {
+  if (!Array.isArray(arr)) {
+    throw new TypeError('Input must be an array')
+  }
+
+  if (!arr.every((item) => typeof item === 'number')) {
+    throw new TypeError('All elements must be numbers')
+  }
+
+  const prefix = []
+  let sum = 0
+  for (const num of arr) {
+    sum += num
+    prefix.push(sum)
+  }
+  return prefix
+}

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

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+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)
+  })
+})