I was doing youtube clone, during sign up process I got issues with sending data on form-data so my mongoose schema like this:

const { Schema, model } = require("mongoose");

const userSchema = new Schema(
  {
    username: {
      type: String,
      required: true,
    },
    watchHistory: {
      type: [
        {
          video: {
            type: Schema.Types.ObjectId,
            ref: "video",
          },
          lastWatchedPosition: {
            type: Number,
            default: 0,
          },
        },
      ],
      default: [],
    },
    likedVideos: {
      type: [Schema.Types.ObjectId],
      ref: "video",
      default: [],
    },
    email: {
      type: String,
    },
    img: {
      filename: String,
      contentType: String,
      image: Buffer,
    },
  },
  { timestamps: true, versionKey: false }
);

module.exports = model("user", userSchema);

and server validation part :

const Joi = require("joi");

const paramsSchema = Joi.object({
  id: Joi.string().hex().length(24).required(),
});

const watchHistorySchema = Joi.object({
  video: Joi.string().hex().length(24).required(),
  lastWatchedPosition: Joi.number().default(0),
}).options({ allowUnknown: false });

const bodySchema = Joi.object({
  username: Joi.string().min(4).required(),
  watchHistory: Joi.array().items(watchHistorySchema),
  likedVideos: Joi.array()
    .items(Joi.string().hex().length(24).required())
    .default([]),
  email: Joi.string().email(),
  img: Joi.object({
    filename: Joi.string().required(),
    contentType: Joi.string().required(),
    image: Joi.binary().required(),
  }),
}).options({ allowUnknown: false });

async function validateParams(req, res, next) {
  try {
    const validParams = await paramsSchema.validateAsync(req.params);
    next(validParams);
  } catch (err) {
    return res.status(400).send({ msg: err.message });
  }
}

async function validateBody(req, res, next) {
  console.log(req.body); // output - {}
  try {
    const validParams = await bodySchema.validateAsync(req.body);
    next(validParams);
  } catch (err) {
    return res.status(400).send({ msg: err.message });
  }
}

module.exports = { validateParams, validateBody };

routes part :

const router = require("express").Router();
const { getAll, getOne, editOne, deleteOne } = require("../controllers/user");
const { signup, login } = require('../utils/auth')
const { validateParams, validateBody } = require('../validations/user')
const multer = require("multer");
const storage = multer.memoryStorage();
const upload = multer({ storage });

router.route("/signup").post( validateBody, upload.single('img'), signup);

router.route("/").get(getAll);

router.route("/:id").get(validateParams, getOne);

router.route("/:id").patch(validateParams, editOne);

router.route("/:id").delete(validateParams, deleteOne);

module.exports = router;

and finally index.js

const expr = require("express");
const app = expr();
const { config } = require("dotenv");
const session = require("express-session");
const DB = require("./settings/DB/db");
const allRoutes = require("./router");
const bodyParser = require("body-parser");
config();
DB();

app.use(bodyParser.json());
app.use(bodyParser.urlencoded())
// app.use(expr.json())

app.use(
  session({
    secret: process.env.SESSION_SECRET,
    resave: false,
    saveUninitialized: false,
  })
);

app.use("/api", allRoutes);

// Global error handler middleware
app.use((err, req, res, next) => {
  if (err) {
    console.log(err, "-err");
    res.status(500).json({ message: `Internal Server Error` });
  }
  next();
});

app.listen(process.env.PORT, () => {
  console.log(`${process.env.PORT}'s port online...`);
});

postman screenshot

when I remove validation from routes it’s working fine, also checked validation, and all things fine.
Main problem’s working with form-data.