auth.service.ts

import * as UserService from "./user.service";

export const register = async (email: string, password: string): Promise<User> =>{
    const user = await UserService.findByEmail(email);
    if(user){
        throw new Error("An account with this email already exists.")
    }

    //Continue Logic
}

user.service.ts

export const findByEmail = async (email: string): Promise<User> => {
    // Some Logic
}