CODE EXAMPLE FOR TYPESCRIPT

express class validator

// using like this 
// this.router.post('/register', [validator([DTORegister])], this.registerUsersController)

export function validator(DataTransferObject: any) {
  return async function (req: Request, res: Response, next: NextFunction): Promise<OutgoingMessage> {
    let errors: any = []

    DataTransferObject.forEach(async (DTO: any) => {
      const property: Record<string, any> = {}
      Object.assign(property, req.body, req.params, req.query)
      const errorsResponse: ValidationError[] = await validate(Object.assign(new DTO(), property))
      errors.push(errorsResponse)
    })

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