元素计数器与JavaScript中的过滤器

debugcn 发表于 Dev

Lex27

我有两个数组，需要返回带有元素和计数器的map对象。它几乎完成了，但是我坚持使用计数器-对于计数器> 1的元素，它始终“未定义”。谁能帮我？

const stopWords = ['', 'a', 'the', 'and', 'or'];
const pageWords = ['HellO', 's', 'And', 'hellO', '', 'AnD', 'NAME', 'oR', 'apple', 'HELLO', 'aPple'];

const wordsCount = (words, stopWords) => {
  const all = new Map();
  const arr = words.map(word => word.toLowerCase())
    .filter(word => !stopWords.includes(word))
    .reduce((acc, word) => {
         const count = all.has(word) ? acc[word] + 1 : 1;
         all.set(word, count);
         return acc;
    }, {});
   return all;
};

//what I need:  [['hello', 3], ['s', 1], ['name', 1], ['apple', 2]]

布雷特·德伍德迪

你超级亲密。我相信现有代码的唯一问题是如何访问的当前计数word。而不是使用，acc[word]您应该使用all.get(word)访问现有计数。像这样：

const stopWords = ['', 'a', 'the', 'and', 'or'];
const pageWords = ['HellO', 's', 'And', 'hellO', '', 'AnD', 'NAME', 'oR', 'apple', 'HELLO', 'aPple'];

const wordsCount = (words, stopWords) => {
  const all = new Map();
  const arr = words.map(word => word.toLowerCase())
    .filter(word => !stopWords.includes(word))
    .reduce((acc, word) => {
         const count = all.has(word) ? all.get(word) + 1 : 1;
         all.set(word, count);
         return acc;
    }, {});
   return all;
};

console.log(Array.from(wordsCount(pageWords, stopWords)))

另外，此更改意味着您不再需要acc，所以reduce我认为aforEach使得代码更易于阅读。像这样：

const stopWords = ['', 'a', 'the', 'and', 'or'];
const pageWords = ['HellO', 's', 'And', 'hellO', '', 'AnD', 'NAME', 'oR', 'apple', 'HELLO', 'aPple'];

const wordsCount = (words, stopWords) => {
  const all = new Map();
  words.map(word => word.toLowerCase())
    .filter(word => !stopWords.includes(word))
    .forEach(word => {
      const count = all.has(word) ? all.get(word) + 1 : 1;
      all.set(word, count);
    });
  
  return all;
};

console.log(Array.from(wordsCount(pageWords, stopWords)));

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