Simple input validation for Express with Joi and Celebrate

user.route.ts

import { Joi, Segments } from "celebrate";
import express from "express";
import type { NextFunction, Request, Response } from "express";

// import our validator
import {
  contentTypeApplicationJsonValidator,
  validator
} from "./validator";

// For example
import { CreateUserDto } from "./dto/create-user.dto.ts";


const router = express.Router();

router.post(
  "/",
  contentTypeApplicationJsonValidator,
  validator({
    [Segments.BODY]: Joi.object({
      login: Joi.string().required(),
      password: Joi.string().required(),
      email: Joi.string().email().required(),
      type: Joi.string(),
      difficultField: Joi.when("type", {
        is: "cool", // For Example
        then: Joi.string()
          .valid("valid", "valid_2")
          .required(),
        otherwise: Joi.forbidden()
      })
    }).required()
  }),
  async (
    req: Request<any, any, CreateUserDto>,
    res: Response,
    next: NextFunction
  ) => {
    try {
      res.sendStatus(200);
    } catch (err) {
      next(err);
    }
  }
);

validator.ts

import type { SchemaOptions, CelebrateOptions } from "celebrate";
import { celebrator, Modes } from "celebrate";
import type { ValidationOptions } from "joi";
import type { RequestHandler } from "express";
import _ from "lodash";


export function validator(
  schema: SchemaOptions,
  celebrateOptions?: CelebrateOptions,
  joiOptions?: ValidationOptions
): RequestHandler {
  return celebrator(
    _.merge({ mode: Modes.FULL } as CelebrateOptions, celebrateOptions),
    _.merge(
      { abortEarly: false, convert: true } as ValidationOptions,
      joiOptions
    ),
    schema
  );
}

// Simple reusable validator
export const contentTypeApplicationJsonValidator = validator({
  [Segments.HEADERS]: Joi.object({
    "content-type": Joi.string().valid("application/json", "application/json; charset=utf-8").required()
  }).unknown()
});