javascript - javascript 中带有过滤器的元素计数器

Question

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，但我卡在了 counter - 对于 counter>1 的元素，它总是“未定义”。谁能帮我吗？

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]]

Answer 1

你们非常接近。我相信您现有代码的唯一问题是您如何访问单词的当前计数。您应该使用 all.get(word) 来访问现有计数，而不是使用 acc[word]。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)))

此外，此更改意味着您不再需要 acc，因此我认为 forEach 可以代替 reduce 使代码变得有点更容易阅读。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)));