Calculator for app development cost estimation using Full-Stack JavaScript developers (MEAN/MERN stacks) in Singapore, Japan, and the UK for Online Booking System applications. This calculator is tailored for apps facilitating reservations for services like appointments, accommodations, tours, or rentals. Full-stack JavaScript (MongoDB, Express.js, Angular/React, Node.js) allows for cohesive development across the frontend and backend. Developer rates in Singapore, Tokyo (JP), and London (UK) will be factored in. Key features influencing cost include dynamic calendar displays for availability, multi-step booking forms, secure payment processing, user account management with booking history, automated confirmation emails and reminders, and admin panels for managing bookings and availability. The calculator will consider the complexity of pricing rules (e.g., seasonal, group discounts), resource management (e.g., number of available rooms, staff schedules), and integration with third-party calendar services or existing business systems. Real-time updates to availability are critical. Backend development must ensure data integrity and secure handling of payments and personal information. Localization for different languages and currencies may be needed. Ongoing costs include system maintenance, updates for new features (e.g., review systems, loyalty programs), and customer support.