在NodeJS的回调中返回布尔值或字符串

const fs = require('fs');

function readFileAndProcess(filePath, callback) {
  fs.readFile(filePath, 'utf8', (err, data) => {
    if (err) {
      return callback(err);
    }

    // 假设我们要检查文件内容是否包含特定字符串
    const containsSpecificString = data.includes('example');

    if (containsSpecificString) {
      callback(null, 'File contains the specific string');
    } else {
      callback(null, false);
    }
  });
}

readFileAndProcess('example.txt', (err, result) => {
  if (err) {
    console.error('Error:', err);
  } else {
    console.log('Result:', result);
  }
});

const readFileAsync = (filePath) => {
  return new Promise((resolve, reject) => {
    fs.readFile(filePath, 'utf8', (err, data) => {
      if (err) {
        reject(err);
      } else {
        resolve(data);
      }
    });
  });
};

async function readFileAndProcessAsync(filePath) {
  try {
    const data = await readFileAsync(filePath);
    const containsSpecificString = data.includes('example');
    return containsSpecificString ? 'File contains the specific string' : false;
  } catch (err) {
    console.error('Error:', err);
  }
}

readFileAndProcessAsync('example.txt').then(result => {
  console.log('Result:', result);
});

fs.readFile(filePath, 'utf8', (err, data) => {
  if (err) {
    console.error('Error:', err);
    return callback(err);
  }
  // 处理数据
});