completed 4.4

parts/4/blogApp/src/utils.js

@@ -15,8 +15,21 @@ const listHelper = (posts) => {
   return 1;
 };
 
+const totalLikes = (posts) => {
+  if (!posts) {
+    return 0;
+  }
+
+  const likeCount = posts
+    .map((post) => post.likes)
+    .reduce((cum, value) => cum + value, 0);
+
+  return likeCount;
+};
+
 module.exports = {
   reverse,
   average,
   listHelper,
+  totalLikes,
 };

parts/4/blogApp/tests/totalLikes.test.js

@@ -0,0 +1,43 @@
+const { test, describe } = require("node:test");
+const assert = require("node:assert");
+const { totalLikes } = require("../src/utils");
+
+describe("total likes ", () => {
+  const posts = [
+    {
+      _id: "5a422aa71b54a676234d17f8",
+      title: "Go To Statement Considered Harmful",
+      author: "Edsger W. Dijkstra",
+      url: "https://homepages.cwi.nl/~storm/teaching/reader/Dijkstra68.pdf",
+      likes: 5,
+      __v: 0,
+    },
+    {
+      _id: "5a422aa71b54a676234d17f8",
+      title: "Go To Statement Considered Harmful",
+      author: "Edsger W. Dijkstra",
+      url: "https://homepages.cwi.nl/~storm/teaching/reader/Dijkstra68.pdf",
+      likes: 2,
+      __v: 0,
+    },
+  ];
+
+  const emptyArray = [];
+
+  const gibberish = "asdaSd123asd";
+
+  test("counts likes properly", () => {
+    assert.strictEqual(totalLikes(posts), 7);
+  });
+
+  test("works fine with empty array", () => {
+    assert.strictEqual(totalLikes(emptyArray), 0);
+  });
+
+  test("fails with gibberish input", () => {
+    const failedCall = () => {
+      totalLikes(gibberish);
+    };
+    assert.throws(failedCall, Error);
+  });
+});

parts/4/notes.md

@@ -2,3 +2,5 @@ Exercises:
 * [X] 4.1
 * [X] 4.2
 * [X] 4.3
+* [X] 4.4
+*