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Viktor Fonic, JavaScript Developer in Zagreb, Croatia
Viktor Fonic

JavaScript Developer in Zagreb, Croatia

Member since July 27, 2013
With a master's degree in computer science and over a decade of experience in full-stack development and eCommerce, Viktor has the knowledge and experience to solve complex problems and build fast, scalable applications working in any role from individual developer to team leader.
Viktor is now available for hire



  • JavaScript, 7 years
  • Ruby on Rails (RoR), 5 years
  • Heroku, 4 years
  • Shopify, 3 years
  • RSpec, 3 years
  • React, 2 years
Zagreb, Croatia



Preferred Environment

Mac, Sublime Text, Git

The most amazing... I've developed is a pharmaceuticals app used to diagnose patients based on their symptoms and medical history.


  • Shopify App Developer

    2017 - PRESENT
    AllNet Apps
    • Built a common, shared codebase framework to reuse across all apps.
    • Since the launch, both apps have had exclusively 5-star reviews.
    Technologies: Ruby on Rails, Shopify API, JavaScript
  • Full-stack Software Developer

    2017 - 2017
    • Implemented long tasks running in the background.
    • Created recurring events schedules and management.
    • Increased database performance.
    • Built drag-n-drop management of homepage blocks.
    • Implemented reusable search components and used them to search and filter multiple types of records.
    Technologies: React, Meteor, Mongo
  • Shopify Developer

    2017 - 2017
    TopGlas GmbH
    • Completely rewrote the shop's main selling point, Konfigurator, to use a more modern state machine pattern (similar to Redux).
    • Developed a page composer tool that transforms Shopify store CMS functionality into a drag-n-drop interface for building-block style construction of shop pages.
    • Optimized JS and CSS delivery, which reduced page size and increased page download speeds by ~50%.
    • Improved "Add to cart" speed by 6x.
    • Implemented custom user click tracking.
    • Implemented user account pages where the user can manage orders, addresses, and other account information.
    • Performed SEO audits.
    Technologies: Shopify Liquid, HTML, SCSS, JS
  • Shopify Developer

    2016 - 2016
    Sitar s.r.l.
    • Built a new Shopify experience from the ground up.
    • Migrated existing shop data from the old PrestaShop installation.
    • Integrated a subscriptions app with "unsupported" QuickView - made it work.
    Technologies: Shopify Liquid, HTML, SCSS, JS
  • Full-stack Ruby on Rails Developer

    2015 - 2016
    DVELP, Ltd.
    • Rebuilt the sign-up flow into a single-page multi-step React form that saw a 5x increase in conversion.
    • Introduced React and Redux technologies to the company.
    • Wrote an open-source SEO plugin for Ruby on Rails apps.
    • Introduced a Shopify theme development template for faster theme development.
    • Built several custom Ruby on Rails apps from the ground up.
    Technologies: Ruby on Rails, React, Redux, RSpec, Heroku, PostgreSQL
  • Software Engineer

    2014 - 2015
    Microsoft Ireland R&D
    • Integrated a TypeScript testing framework into the build system to improve development reliability.
    • Implemented a website redesign that increased the number of installs by over 5% (+20,000 users).
    • Worked on the organization of a company-wide hackathon (120,000 employees, more than 100 hackathon projects, worldwide event).
    • Nominated as employee of the year after the first ten months of employment.
    Technologies: C#, TypeScript, JavaScript, jQuery
  • Full-stack Ruby on Rails Developer

    2013 - 2013
    Music Delta
    • Reduced the number of database queries by 80%.
    • Implemented a sustainable authorization system.
    • Fixed security issues and other various bugs.
    • Completely rewrote the administration interface, improving speed, usability, and security.
    • Added application monitoring.
    Technologies: Ruby on Rails
  • Full-stack Ruby on Rails Developer

    2012 - 2013
    Do the Life
    • Developed a highly scalable solution for generating user schedules with a heuristic algorithm.
    • Integrated the Ruby on Rails application with a Java worker to improve the algorithm's performance.
    • Implemented a natural language parser, allowing users to describe events in natural language.
    • Implemented a tutorial/website tour for first-time login and introduction to new features.
    • Handled cross-time zone event synchronization.
    • Implemented a "Coming Soon" landing page with user sign-up.
    • Implemented a cron process to handle recurring jobs with periodic execution.
    Technologies: Ruby on Rails
  • Software Developer

    2010 - 2013
    Sitar s.r.l.
    • Developed several custom-made pharmaceutical applications to perform diagnosis predictions.
    • Created a specific user-management application for managing user licenses.
    • Gained experience working with a foreign client.
    • Implemented a completely automatic update system with no need for user action when new data or application versions were made available.
    • Created specific database management application for pharmacists to insert data with a single click.
    • Built a dynamic GUI with vector graphics to function appropriately across all screen resolutions.
    Technologies: Java
  • Software Developer

    2011 - 2011
    Netgen d.o.o.
    • Created an API to integrate the ShoutEm platform with eZ Publish CMS.
    • Worked with eZ Publish CMS internals for better tailoring of content to ShoutEm users.
    • Gained significant experience with the eZ Publish CMS and ShoutEm API.
    Technologies: PHP, JavaScript


  • Do The Life (Development)

    Do The Life is a Ruby on Rails virtual secretary web application.

  • GitHub Account (Development)

    A collection of code samples and contributions to open-source projects.

  • Liceknjiga (Development)

    Liceknjiga is a Ruby on Rails social network for sharing photos with privacy, likes, comments, and friends functionality. For more information, see

  • Todolist (Development)

    A TODO application which demonstrates how one might connect AngularJS with a Ruby on Rails back-end for authentication and usage. Additionally, includes an API for mobile application access.

  • Gekwetter (Development)

    A simple Twitter clone written in Ruby on Rails.

  • Water Logic (Development)

    Solution for pouring water game for web, cross-compiled to JS from C++ with Emscripten.




  • Languages

    JavaScript, Sass
  • Frameworks

    ZURB Foundation, Jasmine, Redux, Bootstrap, Ruby on Rails (RoR)
  • Libraries/APIs

    React, Shopify API, Chai, jQuery
  • Tools

    RSpec, Mocha
  • Paradigms

    Agile Software Development
  • Platforms

    Meteor, Shopify, Heroku, WordPress
  • Storage

    MongoDB, PostgreSQL
  • Other

    Apps, Shopify Customizations


  • Master's degree in Computer Science
    2011 - 2013
    University of Zagreb - Zagreb, Croatia
  • Bachelor's degree in Software Engineering
    2007 - 2011
    University of Zagreb - Zagreb, Croatia
  • Bachelor's degree in Software Engineering
    2009 - 2010
    University of Maribor - Maribor, Slovenia
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