4.7. mostLikes function

Pretty much copy paste from mostBlogs

Author: erikpeik

part4/tests/mostLikes.test.js

@@ -0,0 +1,27 @@
+const listHelper = require('../utils/list_helper')
+const arrays = require('./arrays')
+
+describe('most likes', () => {
+  test('of empty list is empty object', () => {
+    const result = listHelper.mostLikes([])
+    expect(result).toEqual({})
+  })
+
+  test('when list has only one blog that author and amount of likes matches', () => {
+    const result = listHelper.mostLikes(arrays.listWithOneBlog)
+    const expected = {
+      author: arrays.listWithOneBlog[0].author,
+      likes: arrays.listWithOneBlog[0].likes,
+    }
+    expect(result).toEqual(expected)
+  })
+
+  test('with multiple blogs is calculated right', () => {
+    const result = listHelper.mostLikes(arrays.blogs)
+    const expected = {
+      author: 'Edsger W. Dijkstra',
+      likes: 17,
+    }
+    expect(result).toEqual(expected)
+  })
+})

part4/utils/list_helper.js

@@ -27,9 +27,26 @@ const mostBlogs = (blogs) => {
   return { author: max, blogs: authors[max] }
 }
 
+const mostLikes = (blogs) => {
+  if (blogs.length === 0) return {}
+
+  const reducer = (max, item) => {
+    max[item.author]
+      ? (max[item.author] += item.likes)
+      : (max[item.author] = item.likes)
+    return max
+  }
+  const authors = blogs.reduce(reducer, {})
+  const max = Object.keys(authors).reduce((a, b) =>
+    authors[a] > authors[b] ? a : b
+  )
+  return { author: max, likes: authors[max] }
+}
+
 module.exports = {
   dummy,
   totalLikes,
   favoriteBlog,
   mostBlogs,
+  mostLikes,
 }