completed exercise 4.7

parts/4/blogApp/src/utils.js

@@ -52,7 +52,6 @@ const mostPosts = (posts) => {
     return acc;
   }, {});
 
-  // Use Object.entries to find the top author
   const [author, postsCount] = Object.entries(countMap).reduce(
     (max, entry) => (entry[1] > max[1] ? entry : max),
     ['', 0]
@@ -61,6 +60,24 @@ const mostPosts = (posts) => {
   return { author, posts: postsCount };
 };
 
+const mostLikes = (posts) => {
+    if (!posts || posts.length === 0) {
+      return null;
+    }
+  
+    const likesMap = posts.reduce((acc, post) => {
+      acc[post.author] = (acc[post.author] || 0) + post.likes;
+      return acc;
+    }, {});
+  
+    const [author, likesCount] = Object.entries(likesMap).reduce(
+      (max, entry) => (entry[1] > max[1] ? entry : max),
+      ['', 0]
+    );
+  
+    return { author, likes: likesCount };
+  };
+
 module.exports = {
   reverse,
   average,
@@ -68,4 +85,5 @@ module.exports = {
   totalLikes,
   favoritePost,
   mostPosts,
+  mostLikes
 };

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

@@ -0,0 +1,54 @@
+const { test, describe } = require("node:test");
+const assert = require("node:assert");
+const { mostLikes } = require("../src/utils");
+
+describe("most 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,
+    },
+    {
+      _id: "123",
+      title: "Lololo",
+      author: "John Doe",
+      url: "https://homepages.cwi.nl/~storm/teaching/reader/Dijkstra68.pdf",
+      likes: 1,
+      __v: 0,
+    },
+  ];
+
+  const emptyArray = [];
+
+  const gibberish = "asdaSd123asd";
+
+  test("finds top author  properly", () => {
+    assert.deepStrictEqual(mostLikes(posts), {
+      author: "Edsger W. Dijkstra",
+      likes: 7,
+    });
+  });
+
+  test("works fine with empty array", () => {
+    assert.strictEqual(mostLikes(emptyArray), null);
+  });
+
+  test("fails with gibberish input", () => {
+    const failedCall = () => {
+      mostLikes(gibberish);
+    };
+    assert.throws(failedCall, Error);
+  });
+});