javascript - 如何读取 Node 中的两个文件并检查两个文件中是否存在单词

Question

这个问题已经有答案了:

Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference (7 个回答)

已关闭 4 年前。

我正在尝试 Node 中的新事物，所以这里我想读取两个文件并检查文件中的所有单词是否相同。

示例:两个相似的文件，其中一个文件添加了一些额外的单词。

因此，在检查两个文件后，如果一个文件中的单词在另一个文件中不存在，则应该打印出这些单词

这是我到目前为止所尝试过的，但这似乎没有按预期工作，而且不是正确的方法

let newData = [];
let oldData = [];

(async () => {
  await new Promise(resolve => {
    fs.readFile(
      pathname.join(__dirname, "public", "hello.txt"),
      (err, data) => {
        const wordsInFile = data.toString().toLowerCase();
        // Here we should split string by some delimiter for further words processing. Assume, that your file looks like this "word1 word2". We'll use space delimiter.
        newData = wordsInFile.split(" ");
        resolve();
      }
    );
  });

  // here is the same code for the second file. Or you can move code to another function.
  await new Promise(resolve => {
    fs.readFile(pathname.join(__dirname, "public", "test.txt"), (err, data) => {
      const wordsInFile = data.toString().toLowerCase();
      // Here we should split string by some delimiter for further words processing. Assume, that your file looks like this "word1 word2". We'll use space delimiter.
      newData = wordsInFile.split(" ");
      resolve();
    });
  });
  // And now we can use Set from ES6, to find intersection/difference etc.
  const wordsNotInFileAndNotInFileTwo = new Set(
    [...newData].filter(x => !oldData.has(x))
  );
  console.log(wordsNotInFileAndNotInFileTwo);

  // But you can simple iterate two arrays to achieve your goal.
})();

如有任何帮助，我们将不胜感激

Answer 1

嵌套readFile:

fs.readFile(pathname.join(__dirname, "public", "hello.txt"), (err, data) => {
  newData = data.toString().toLowerCase();
  fs.readFile(pathname.join(__dirname, "public", "test.txt"), (err, data) => {
    oldData = data.toString().toLowerCase();
    if (newData === oldData) {
      console.log("Same");
    } else {
      console.log("Not Same");
      const a = newData.split(' ')
      const b = oldData.split(' ')

      const result = a.filter(w => !oldData.includes(w));
      console.log(result.join(' '));
    }
  });
});

这样，内部函数中的回调就可以访问外部函数中设置的变量。