如何在multer中检查文件类型

npm install --save multer multer-s3 aws-sdk

const multer = require('multer');
const multerS3 = require('multer-s3');
const AWS = require('aws-sdk');

AWS.config.update({
  accessKeyId: 'YOUR_ACCESS_KEY',
  secretAccessKey: 'YOUR_SECRET_ACCESS_KEY',
  region: 'YOUR_REGION'
});

const s3 = new AWS.S3();
const upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: 'YOUR_BUCKET_NAME',
    acl: 'public-read', // 设置文件的访问权限
    metadata: function (req, file, cb) {
      cb(null, { fieldName: file.fieldname });
    },
    key: function (req, file, cb) {
      cb(null, Date.now().toString()) // 设置文件名为当前时间戳
    }
  }),
  fileFilter: function (req, file, cb) {
    // 检查文件类型
    if (file.mimetype !== 'image/jpeg' && file.mimetype !== 'image/png') {
      return cb(new Error('Only JPEG and PNG files are allowed'));
    }
    cb(null, true);
  }
});

app.post('/upload', upload.single('file'), function (req, res, next) {
  // 文件上传成功后的处理逻辑
  res.send('File uploaded successfully');
});