feat(sumNestedArray): Add sumNestedArray module

Author: sargalias

src/recursion-practice/sumNestedArray/sumNestedArray.js

@@ -0,0 +1,34 @@
+import { identity } from '../utils';
+
+const sumNestedArrayIter = arr => {
+  let sum = 0;
+  arr.forEach(el => {
+    if (Array.isArray(el)) {
+      sum += sumNestedArrayIter(el);
+    } else {
+      sum += el;
+    }
+  });
+  return sum;
+};
+
+const sumNestedArray = ([n1, ...rest]) => {
+  if (n1 === undefined) return 0;
+
+  const n1Result = Array.isArray(n1) ? sumNestedArray(n1) : n1;
+  const restResult = sumNestedArray([...rest]);
+  return n1Result + restResult;
+};
+
+const sumNestedArrayCPS = ([n1, ...rest], cont = identity) => {
+  if (n1 === undefined) return cont(0);
+
+  const cb = Array.isArray(n1)
+    ? restResult =>
+        sumNestedArrayCPS([...n1], n1Result => cont(n1Result + restResult))
+    : restResult => cont(n1 + restResult);
+
+  return sumNestedArrayCPS([...rest], cb);
+};
+
+export { sumNestedArrayIter, sumNestedArray, sumNestedArrayCPS };

src/recursion-practice/sumNestedArray/sumNestedArray.test.js

@@ -0,0 +1,25 @@
+import each from 'jest-each';
+import {
+  sumNestedArray,
+  sumNestedArrayCPS,
+  sumNestedArrayIter,
+} from './sumNestedArray';
+
+[sumNestedArrayIter, sumNestedArray, sumNestedArrayCPS].forEach(fn => {
+  describe(`${fn.name}`, () => {
+    each`
+      arr                             | expected
+      ${[]}                           | ${0}
+      ${[1]}                          | ${1}
+      ${[1, 2, 3, 4, 5]}              | ${15}
+      ${[1, [2, 3], 4, 5]}            | ${15}
+      ${[1, [2, [3], 4], 5]}          | ${15}
+      ${[1, [], [2, [], [3], 4], 5]}  | ${15}
+    `.test(
+      'should return $expected when called with $arr',
+      ({ arr, expected }) => {
+        expect(fn(arr)).toBe(expected);
+      },
+    );
+  });
+});