使用Node JS和axios下载文件并确定MIME类型，文件类型

const axios = require('axios');
const fs = require('fs');
const path = require('path');

async function downloadFile(url, outputPath) {
  const response = await axios({
    url: url,
    method: 'GET',
    responseType: 'stream'
  });

  const contentType = response.headers['content-type'];
  const extension = getExtensionFromContentType(contentType);
  const fileName = `file.${extension}`;
  const filePath = path.join(outputPath, fileName);

  const writer = fs.createWriteStream(filePath);
  response.data.pipe(writer);

  return new Promise((resolve, reject) => {
    writer.on('finish', () => resolve(filePath));
    writer.on('error', reject);
  });
}

function getExtensionFromContentType(contentType) {
  const mimeTypes = {
    'image/jpeg': 'jpg',
    'image/png': 'png',
    'image/gif': 'gif',
    'application/pdf': 'pdf',
    // 添加更多MIME类型和文件扩展名的映射
  };

  const defaultExtension = 'unknown';

  if (contentType && mimeTypes[contentType]) {
    return mimeTypes[contentType];
  }

  return defaultExtension;
}

// 示例用法
const fileUrl = 'https://example.com/file.jpg'; // 要下载的文件的URL
const outputPath = '/path/to/output'; // 下载文件的输出路径

downloadFile(fileUrl, outputPath)
  .then(filePath => {
    const mimeType = getMimeTypeFromFilePath(filePath);
    console.log(`文件下载成功，MIME类型: ${mimeType}`);
  })
  .catch(error => {
    console.error('文件下载失败:', error);
  });