JavaScript 对象无法被其识别属性

Question

我的程序非常简单 - 它应该将电影保存在数组中，然后以 JSON 格式打印它们。问题在于 'contains()' 方法（我认为）。它适用于一个命名的电影，但当名称包含空格时它 returns null。这是代码。

function movieDirectors(array) {
  let movies = [];

  class Movie {
    constructor(name, director, date) {
      this.name = name;
      this.director = director;
      this.date = date;
    }
  }
  let contains = function (movieName) {
    let movie = null;
    movies.forEach(m => m.name === movieName ? movie = m : movie = null);
    return movie;
  }

  for (let i = 0; i < array.length; i++) {
    let command = array[i].split(' ');

    if (command.includes('addMovie')) {
      let name = command.slice(1, command.length).join(' ');
      movies.push(new Movie(name, null, null));
    } else if (command.includes('directedBy')) {
      let name1 = command.slice(0, command.indexOf('directedBy')).join(' ');
      if (contains(name1) !== null) {
        let movie = contains(name1);
        movie.director = command.slice(command.indexOf('directedBy') + 1, command.length).join(' ');
      }
    } else if (command.includes('onDate')) {
      let name2 = command.slice(0, command.indexOf('onDate')).join(' ');
      if (contains(name2) !== null) {
        let movie = contains(name2);
        movie.date = command.slice(command.indexOf('onDate') + 1, command.length).join(' ');
      }
    }
  }
  movies.forEach(m => m.director != null && m.name != null && m.date != null ? console.log(JSON.stringify(m)) : null);
}

movieDirectors([
    'addMovie Fast and Furious',
    'addMovie Godfather',
    'Godfather directedBy Francis Ford Coppola',
    'Godfather onDate 29.07.2018',
    'Fast and Furious onDate 30.07.2018',
    'Fast and Furious directedBy Rob Cohen']);

输出必须是这样的：

{"name":"Fast and Furious","date":"30.07.2018","director":"Rob Cohen"}
{"name":"Godfather","director":"Francis Ford Coppola","date":"29.07.2018"}

我在 JavaScript 语言方面还很新手，如果能帮助我理解这门语言的这些优点，我将不胜感激。

Answer 1

问题是您在 contains() 中制作 forEach 的方式。

你有：

movies.forEach(m => m.name === movieName ? movie = m : movie = null);

您的 movies 数组首先填充 Fast and Furious，然后填充 Godfather。在 forEach 的第一次迭代中，它将测试 Fast and Furious 并发现它等于 movieName，因此 movie = m 您的代码将使用正确的对象设置 movie。在第二次迭代中，它将运行与 Godfather 进行相同的测试，并发现它与 movieName 不同，因此 movie = null 您的代码将清除 movie，这就是错误。相反，让您的代码在 m.name === movieName 为 false 时不执行任何操作。所以：

movies.forEach(m => m.name === movieName ? movie = m : null);

这是完整的工作片段：

function movieDirectors(array) {
  let movies = [];

  class Movie {
    constructor(name, director, date) {
      this.name = name;
      this.director = director;
      this.date = date;
    }
  }
  let contains = function (movieName) {
    let movie = null;
    movies.forEach(m => m.name === movieName ? movie = m : null); // The problem was here
    return movie;
  }

  for (let i = 0; i < array.length; i++) {
    let command = array[i].split(' ');

    if (command.includes('addMovie')) {
      let name = command.slice(1, command.length).join(' ');
      movies.push(new Movie(name, null, null));
    } else if (command.includes('directedBy')) {
      let name1 = command.slice(0, command.indexOf('directedBy')).join(' ');
      if (contains(name1) !== null) {
        let movie = contains(name1);
        movie.director = command.slice(command.indexOf('directedBy') + 1, command.length).join(' ');
      }
    } else if (command.includes('onDate')) {
      let name2 = command.slice(0, command.indexOf('onDate')).join(' ');
      if (contains(name2) !== null) {
        let movie = contains(name2);
        movie.date = command.slice(command.indexOf('onDate') + 1, command.length).join(' ');
      }
    }
  }
  movies.forEach(m => m.director != null && m.name != null && m.date != null ? console.log(JSON.stringify(m)) : null);
}

movieDirectors([
    'addMovie Fast and Furious',
    'addMovie Godfather',
    'Godfather directedBy Francis Ford Coppola',
    'Godfather onDate 29.07.2018',
    'Fast and Furious onDate 30.07.2018',
    'Fast and Furious directedBy Rob Cohen']);

Answer 2

由于您的问题主要与字符串解析有关，您可以使用如下正则表达式来解决它：

const input = [
  'addMovie Fast and Furious',
  'addMovie Godfather',
  'Godfather directedBy Francis Ford Coppola',
  'Godfather onDate 29.07.2018',
  'Fast and Furious onDate 30.07.2018',
  'Fast and Furious directedBy Rob Cohen'
];

const output = input.reduce((acc, cur) => {
    const parseAddMovie = /^addMovie\s(.+)/.exec(cur);
    if (parseAddMovie) {
      const [, name] = parseAddMovie;
      acc.push({ name });
      return acc;
    }
    const parseDirectedBy = /(.+)\sdirectedBy\s(.+)/.exec(cur);
    if (parseDirectedBy) {
      const [, name, director] = parseDirectedBy;
      const found = acc.find(x => x.name === name);
      found && (found.director = director);
      return acc;
    }
    const parseOnDate = /(.+)\sonDate\s(.+)/.exec(cur);
    if (parseOnDate) {
      const [, name, date] = parseOnDate;
      const found = acc.find(x => x.name === name);
      found && (found.date = date);
      return acc;
    }
  }, []);

console.log(output);

Answer 3

函数 contains 预计会停止，并且 return 会在找到具有给定名称的电影时停止。

它将起作用：

let contains = function (movieName) {
    return movies.find(m => m.name === movieName);
}

JavaScript 对象无法被其识别属性

JavaScript Objects is not recognised by it's property

javascript

arrays

properties

function

object

JavaScript 对象无法被其识别 属性

JavaScript Objects is not recognised by it's property

javascript

arrays

properties

function

object

JavaScript 对象无法被其识别属性