Handling File Uploads

import multer from "multer";

// Memory — file in req.file.buffer
const memUpload = multer({ storage: multer.memoryStorage() });

// Disk — file persisted to disk
const diskUpload = multer({
  storage: multer.diskStorage({
    destination: "./uploads",
    filename: (req, file, cb) => cb(null, `${Date.now()}-${file.originalname}`)
  })
});

app.post("/avatar",
  diskUpload.single("avatar"),  // form field name
  (req, res) => {
    res.json({
      filename: req.file.filename,
      size: req.file.size,
      mime: req.file.mimetype
    });
  }
);

app.post("/photos",
  diskUpload.array("photos", 10),  // max 10 files
  (req, res) => res.json({ count: req.files.length })
);

app.post("/listing",
  diskUpload.fields([
    { name: "cover", maxCount: 1 },
    { name: "gallery", maxCount: 8 }
  ]),
  (req, res) => {
    const cover = req.files.cover?.[0];
    const gallery = req.files.gallery || [];
    res.json({ cover: cover?.filename, gallery: gallery.map(f => f.filename) });
  }
);

const upload = multer({
  storage,
  fileFilter: (req, file, cb) => {
    const allowed = ["image/jpeg", "image/png", "image/webp"];
    if (!allowed.includes(file.mimetype)) {
      return cb(new Error("Only JPEG/PNG/WebP allowed"));
    }
    cb(null, true);
  }
});

const upload = multer({
  storage,
  limits: { fileSize: 5 * 1024 * 1024, files: 1 }
});

import path from "node:path";

fileFilter: (req, file, cb) => {
  const ext = path.extname(file.originalname).toLowerCase();
  const allowedExt = [".jpg", ".jpeg", ".png", ".webp"];
  const allowedMime = ["image/jpeg", "image/png", "image/webp"];
  if (allowedExt.includes(ext) && allowedMime.includes(file.mimetype)) cb(null, true);
  else cb(new Error("Invalid file type"));
}

import { randomUUID } from "node:crypto";

multer.diskStorage({
  destination: "./uploads",
  filename: (req, file, cb) => {
    const ext = path.extname(file.originalname).toLowerCase();
    cb(null, `${randomUUID()}${ext}`);
  }
});

import multer from "multer";

app.post("/upload", upload.single("file"), handler);

app.use((err, req, res, next) => {
  if (err instanceof multer.MulterError) {
    return res.status(400).json({ error: err.code, field: err.field });
  }
  next(err);
});