Express File Upload with Multer

const multer = require("multer");
const path   = require("path");

const upload = multer({
  dest: "uploads/",
  limits: { fileSize: 5 * 1024 * 1024 },
  fileFilter(req, file, cb) {
    const allowed = [".jpg", ".jpeg", ".png", ".pdf"];
    cb(null, allowed.includes(path.extname(file.originalname).toLowerCase()));
  },
});

app.post("/upload", upload.single("file"), (req, res) => {
  res.json({ filename: req.file.filename });
});