为什么这个函数返回{作者：Robert C. Martin，喜欢：NaN}，当数组较大时

Question

const mostLikes = (blogs) => {

  if (!blogs.length) {

    return 0

  }

  const distinctAuthors = [...new Set(blogs.map((blog) => blog.author))]

  const summer = (prev, comp) => prev.likes + comp.likes

  console.log(distinctAuthors)

  const dummyAuth = {

    author: 'hmm',

    likes: 0,

  }

  const authorsWithLikes = distinctAuthors.map((author) => ({

    author,

    likes: blogs.filter((n) => n.author === author).reduce(summer, dummyAuth),

  }))

  const reducer = (prev, comp) => (prev[1] > comp[1] ? prev : comp)

  return authorsWithLikes.reduce(reducer, authorsWithLikes[0])

}

当单个博客大小 === 1 时，工作不工作，但当输入 = >

  const blogs = [{

      _id: '5a422a851b54a676234d17f7',title: 'React patterns', author: 'Michael Chan', url: 'https://reactpatterns.com/', likes: 7, __v: 0,

    }, {

      _id: '5a422aa71b54a676234d17f8', title: 'Go To Statement Considered Harmful', author: 'Edsger W. Dijkstra', url: 'http://www.u.arizona.edu/~rubinson/copyright_violations/Go_To_Considered_Harmful.html', likes: 5, __v: 0,

    }, {

      _id: '5a422b3a1b54a676234d17f9', title: 'Canonical string reduction', author: 'Edsger W. Dijkstra', url: 'http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD808.html', likes: 12, __v: 0,

    }, {

      _id: '5a422b891b54a676234d17fa', title: 'First class tests', author: 'Robert C. Martin', url: 'http://blog.cleancoder.com/uncle-bob/2017/05/05/TestDefinitions.htmll', likes: 10, __v: 0,

    }, {

      _id: '5a422ba71b54a676234d17fb', title: 'TDD harms architecture', author: 'Robert C. Martin', url: 'http://blog.cleancoder.com/uncle-bob/2017/03/03/TDD-Harms-Architecture.html', likes: 0, __v: 0,

    }, {

      _id: '5a422bc61b54a676234d17fc', title: 'Type wars', author: 'Robert C. Martin', url: 'http://blog.cleancoder.com/uncle-bob/2016/05/01/TypeWars.html', likes: 2, __v: 0,

    },

    ]

不知道该怎么办，尝试过实现不同的方法，但现在有点碰壁了。想知道是否有更好的方法？

Answer 1

问题在于夏季减速器。它需要一个包含属性的对象。但是，它返回一个数字。第一次调用 summer 时，它接收具有属性的对象，但是，第二次调用它时，它会收到一个数字（不包含 like 的属性）。likesdummyAuthlikes您可以通过使 summer 返回具有属性的对象来解决此问题。likesconst mostLikes = (blogs) => {  if (!blogs.length) {    return 0;  }  const distinctAuthors = [...new Set(blogs.map((blog) => blog.author))];  const summer = (prev, comp) => ({ likes: prev.likes + comp.likes });  const dummyAuth = {    author: 'hmm',    likes: 0,  }  const authorsWithLikes = distinctAuthors.map((author) => ({    author,    likes: blogs.filter((n) => n.author === author).reduce(summer, dummyAuth ).likes, // note: you have to access the `likes` property   }));  const reducer = (prev, comp) => (prev[1] > comp[1] ? prev : comp);  return authorsWithLikes.reduce(reducer, authorsWithLikes[0]);};

Answer 2

看起来你有未声明的变量：authorblogs.filter((n) => n.author === author)

Answer 3

下面是类型对象，代码尝试用对象添加一个数字。而不是声明为对象，仅以 0 初始化dummyAuthdummyAuthlikesconst blogs = [{  _id: '5a422a851b54a676234d17f7',  title: 'React patterns',  author: 'Michael Chan',  url: 'https://reactpatterns.com/',  likes: 7,  __v: 0,}, {  _id: '5a422aa71b54a676234d17f8',  title: 'Go To Statement Considered Harmful',  author: 'Edsger W. Dijkstra',  url: 'http://www.u.arizona.edu/~rubinson/copyright_violations/Go_To_Considered_Harmful.html',  likes: 5,  __v: 0,}, {  _id: '5a422b3a1b54a676234d17f9',  title: 'Canonical string reduction',  author: 'Edsger W. Dijkstra',  url: 'http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD808.html',  likes: 12,  __v: 0,}, {  _id: '5a422b891b54a676234d17fa',  title: 'First class tests',  author: 'Robert C. Martin',  url: 'http://blog.cleancoder.com/uncle-bob/2017/05/05/TestDefinitions.htmll',  likes: 10,  __v: 0,}, {  _id: '5a422ba71b54a676234d17fb',  title: 'TDD harms architecture',  author: 'Robert C. Martin',  url: 'http://blog.cleancoder.com/uncle-bob/2017/03/03/TDD-Harms-Architecture.html',  likes: 0,  __v: 0,}, {  _id: '5a422bc61b54a676234d17fc',  title: 'Type wars',  author: 'Robert C. Martin',  url: 'http://blog.cleancoder.com/uncle-bob/2016/05/01/TypeWars.html',  likes: 2,  __v: 0,}, ]const mostLikes = (blogs) => {  if (!blogs.length) {    return 0  }  const distinctAuthors = [...new Set(blogs.map((blog) => blog.author))];  const summer = (prev, comp) => prev + comp.likes;  const likes = 0;  const authorsWithLikes = distinctAuthors.map((author) => {    return {      author,      likes: blogs.filter((n) => n.author === author).reduce(summer, likes)    };  });  console.log(authorsWithLikes);  const reducer = (prev, comp) => (prev[1] > comp[1] ? prev : comp);  return authorsWithLikes.reduce(reducer, authorsWithLikes[0])};mostLikes(blogs)