
Nikola Pejčinović
Verified Expert in Engineering
Front-end Developer
Belgrade, Serbia
Toptal member since April 12, 2022
Nikola is an experienced front-end developer specializing in React technology and its ecosystem. To this date, his professional experience includes work on various projects across different industries, from large-scale SaaS apps to small-scope landing pages. Scalability, reusability, and flexibility of software architecture are the main focus of Nikola's programming.
Portfolio
Experience
- CSS - 5 years
- HTML - 5 years
- JavaScript - 5 years
- React - 5 years
- Context API - 4 years
- Redux - 4 years
- TypeScript - 3 years
- Next.js - 2 years
Availability
Preferred Environment
Windows, MacOS, Linux, Visual Studio Code (VS Code), GitHub, JavaScript, Pixel Perfect, Agile
The most amazing...
...project I've built is a reusable UI library used worldwide that improved the scalability and development of a client company's large apps and systems.
Work Experience
Front-end Developer
FPFX Technologies
- Contributed to developing and maintaining cross-project reusable front-end solutions, drastically improving development scalability, decreasing development time, and significantly saving company and clients' budgets.
- Improved application UI using Tailwind CSS with other business-specific 3rd-party tools and libraries (Recharts, RadixUI, React Hook Form, etc.).
- Developed and maintained reusable UI solutions for multi-project mono repositories across different applications.
- Improved application performance by employing SSR rendering strategies of the latest Next.js (13+) versions.
- Collaborated closely with management, operations, and delivery teams to estimate tasks and workload effectively.
- Engineered complex fintech-related calculations, performing data remapping on the front end and creating dynamic data visualizations using the Recharts charting library.
- Resolved critical bug fixes and incidents, ensuring smooth functionality and uptime.
- Took full ownership of the code production lifecycle, from implementation to deployment across multiple environments (staging, development, and production).
- Handled on-call responsibilities as the first responder for critical incidents and was the on-call engineer responsible for production deployments across environments and applications.
- Conducted minor C#/.NET development tasks in coordination with the back-end development team, enhancing and updating existing endpoints, services, controllers, and queries to align with evolving front-end requirements.
Front-end Developer
Kalshi Inc
- Refactored portions of React CSR codebase by employing various Next.js SSR strategies.
- Resolved authentication/authorization issues at the front-end level.
- Improved application UI using Material UI library with other various business-specific 3rd-party tools and libraries.
React Developer
Stubben Edge Group Limited
- Contributed to the development of a complete front-end architecture from the ground up.
- Maintained and improved legacy code by constantly proposing fresh solutions and implementing new features according to industry standards and best practices.
- Resolved time-sensitive critical bug fixes across multiple React-based projects.
Senior Front-end Developer
iptiQ Life S.A. UK
- Developed a reusable analytics tool that monitors customer usage across the whole application using Tealium tag management.
- Created a significant knowledge base for other team members for further development by delivering a proof-of-concept payment solution.
- Contributed to the development of a complete front-end architecture from the ground up.
- Maintained and improved a client's legacy third-party solution integration according to industry standards and best practices.
- Created customized components according to design specifications using the MUI library.
React Developer
Quantox Technology
- Implemented major solutions and critical bug fixes related to cross-browser and cross-device optimization issues, drastically improving the client's customer retention rate and keeping more than 60,000 active users on their platform.
- Developed the project architecture from the ground up.
- Maintained and improved legacy code by constantly proposing new solutions and implementing new features according to industry standards and best practices.
- Helped team members with the challenges faced during the project development process and problem-solving.
- Developed and maintained internal projects and applications and actively contributed to the company's non-commercial endeavors like blockchain hackathons, research and development activities, and workshops.
Lead React Developer (Freelance)
Starcier
- Led a team of three developers in building an enterprise platform.
- Helped and mentored team members with the challenges faced during the project development process and problem-solving.
- Scored a significant client for the company by delivering a time-critical proof-of-concept web app within two months.
- Created a global portal through which all of the client's professionals can gain access to their portfolio companies, a worldwide network of high-profile SMEs and C-level executives, relevant business insights, and research.
- Implemented an authentication infrastructure using the Okta platform.
- Developed a complete front-end architecture from the ground up.
React Developer
JAGGAER
- Created customized components according to design specifications using Material-UI, styled-components, and styled tools libraries.
- Contributed to the development of a core part of the platform—a form designer feature with which users can create custom forms according to their businesses requirements.
- Managed custom application components library and codebase documentation using React Styleguidist.
- Participated in developing and maintaining the overall codebase and project architecture mono repository using Lerna.
- Refactored critical parts of the application into reusable modules and separate npm packages.
- Improved the application's development and maintenance by constantly proposing reusable and performance-oriented solutions.
React Developer (Freelance)
PatronGG
- Implemented an authentication infrastructure using Auth0.
- Created highly customized and reusable React components according to design specifications using the Material-UI library.
- Translated complex business requirements into a well-organized front-end architecture.
- Delivered cross-browser optimization for all application features.
- Built features and functionalities with speed and performance in mind.
Front-end Developer
Teodesk
- Contributed to the design, architecture, and development of a project management application.
- Resolved critical bugs concerning the UI and front-end architecture, which fixed important performance issues.
- Refactored and organized the application's UI codebase using the BEM methodology with Less, making it more scalable and maintainable.
- Implemented a task tracking Gantt chart, which improved the overview and monitoring of the overall project progress through a transparent timeline.
- Ensured the high quality of the project by proposing and implementing enhancements.
- Developed and maintained other internal projects and applications.
Front-end Developer
Diamond Code
- Developed an app that optimized business processes and boosted communication between over 50 clients' operators and employees.
- Built new features across different application modules, drastically improving the overall UI/UX.
- Implemented important bug fixes, which improved the application's customer retention rate.
- Upgraded the codebase by refactoring legacy code and reorganizing the application architecture.
Experience
Tangram iptiQ
https://lifeprotect.zurich.ch/GA Compass
Jaggaer One
https://www.jaggaer.com/solutions/Skills
Libraries/APIs
React, React Redux, Context API, REST APIs, Node.js, Formik, Normalizr, Lodash, React Router, Yup, React Hook Form, Redux-Saga, MobX, Recharts, Zod
Tools
JSX, GitHub, Lerna, Git, Auth0, Webpack, BrowserStack, NPM
Languages
JavaScript, CSS, TypeScript, ECMAScript (ES6), HTML5, HTML, Sass, Less, SCSS, GraphQL, C#.NET
Paradigms
Agile, Test-driven Development (TDD), REST, Responsive Web Design (RWD), Functional Programming, BEM, Unit Testing
Frameworks
Redux, Next.js, Jest, Tailwind CSS, Knockout (Knockout.js), Material UI, Cypress
Platforms
Visual Studio Code (VS Code), Windows, MacOS, Linux, DotCMS, Tealium
Storage
JSON
Other
Front-end, Application State Management, Reusable Libraries, Responsive Design, API Integration, DOM, Single-page Applications (SPAs), Front-end Design, Front-end Development, Styled-components, Storybook, Axios, Enzyme, Pixel Perfect, APIs, User Experience (UX), User Interface (UI), Web Development, WebSockets, Server-side Rendering (SSR), JSDoc, Okta, Tealium iQ Tag Management, Schemas, TradingView, Radix UI, Zustand, FontAwesome, Turborepo
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