CODE EXAMPLE FOR TYPESCRIPT

express class validator

import { validate, ValidationError } from 'class-validator'
import { ClassConstructor, plainToClass } from 'class-transformer'
import { StatusCodes as status } from 'http-status-codes'
import { Request, Response, NextFunction } from 'express'
import { OutgoingMessage } from 'http'

import { apiResponse } from '@helpers/helper.apiResponse'

export function validator(MetaType: ClassConstructor<any>) {
  return async function (req: Request, res: Response, next: NextFunction): Promise<OutgoingMessage> {
    let property: Record<string, any> = {}
    Object.assign(property, req.body, req.params, req.query)

    const object: Record<string, any> = plainToClass(MetaType, property)
    const errorsResponse: ValidationError[] = await validate(object)

    const errorMessage = errorsResponse.map((val: ValidationError) => apiResponse(400, Object.values(val.constraints)[0]))
    if (errorMessage.length) {
      return res.status(status.BAD_REQUEST).json({ errors: errorMessage })
    }
    next()
  }
}