feat: add basic prefix sum implementation with tests

Author: rishima17

Data-Structures/Array/BasicPrefixSum.js

@@ -0,0 +1,24 @@
+/**
+ * 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;
+};