You will find us in Osona, in the province of Barcelona.
Web application development with React
We program the interface of custom web applications with React, separate from the API, so each part can evolve on its own.
Looking for React developers for your web application?
It is the technology we use to build the interface of projects that separate the API and the frontend.
React is the JavaScript library we use to build the interface of custom web applications when the logic lives in a separate API. We usually develop the API with PHP and Slim Framework, and the interface with React and Mantine.
Separating the two parts makes it possible to scale each one independently, connect other tools to the same API, change the look without touching the logic, and write automated tests. It is what we recommend for new projects.
What React is and why we use it
An open-source library, created by Meta, for building interfaces out of components.
React splits the interface into components: independent pieces, such as a form, a table, or a filter, that are programmed once and reused throughout the application. When the data changes, React updates only the part of the screen that depends on it.
We write it in TypeScript, which adds types to the code and catches many errors before it runs. React is one of the most widely used frontend libraries, with a very large community and mature tools, which makes it easier to maintain the application for years.
Advantages of React in a custom web application
Reusable components
Each piece of the interface is programmed once and used on every screen that needs it, with the same behavior.
Interface separate from the logic
The interface consumes an API. The look can change and new screens can be added without touching the business rules.
Automated tests
Components are tested separately: a test warns that something has broken before a user finds out.
Code in TypeScript
Types catch errors while the code is being written and make large changes safer.
Performance
React updates only what changes on screen, and the application is split so each part loads when it is needed.
Community and continuity
Meta and a very large community keep it up to date, and many developers know it.
Where we use React at Gilsys
The same component-based way of programming works for web applications, websites, and mobile apps.
Web applications with Mantine
Admin panels, internal applications, and SaaS tools. To avoid starting from scratch on every screen, we use Mantine, a React component library.
Interactive parts of Astro websites
On websites built with Astro, the interactive parts can be React components that load only when they appear on screen.
Mobile apps with React Native
We apply what we know about React to iOS and Android apps with React Native, with the same component-based way of working.
React development services
From the first screen to the maintenance of applications already in use.
Development from scratch
We program the application's interface from the project requirements, connected to its API and with its tests.
API integration
We connect the interface to the project API and to external services: ERP, CRM, payment gateways, or authentication systems.
Migration to React
We move legacy interfaces, built with jQuery, server-side templates, or unmaintained frameworks, to React, and separate the logic into an API. More information in migration and integration.
Automated tests
Projects with a separate API and frontend include automated tests, which we also write with specialized AI agents, under our review.
Maintenance and evolution
We update React and its dependencies, fix issues, and add features, including in applications developed by another team.
Consulting and advice
We review existing React applications and help decide the architecture of a new project: what goes in the API and what goes in the interface.
If you need React developers, count on Gilsys
From Osona, in the province of Barcelona, we develop web applications with React for companies in any sector.