JavaScript Developer

Fosh; Argentina; Presencial; ARS 2.000.000 - 4.000.000; Jornada completa

Descripción de la vacante

Fosh is seeking a Senior JavaScript Developer to join our international team. You will be responsible for building scalable frontend solutions with React, TypeScript and CSS, participating in architecture, design, development, launching and maintenance of web applications.

You should be proactive, a strong team player, and fluent in English and Spanish. The role involves collaboration with product, design, QA and backend teams, and includes on-call responsibilities.

Formación

• 5+ years of modern frontend development experience with React, TypeScript, and CSS.
• Strong understanding of React patterns, hooks, lifecycle, and rendering behavior.
• Experience with state management tools (Redux Toolkit, Zustand) and web performance.
• Knowledge of SSR frameworks like Next.js and web standards including accessibility.
• Familiarity with CI/CD and automated testing (unit/integration).
• B2 English written and spoken.

Responsabilidades

• Implement scalable, modular frontend solutions using React, TypeScript, and CSS with modern tooling.
• Build features that handle real-time data updates and complex state management.
• Work closely with product, design, quality and backend teams to deliver features with quality and speed.
• Write clean, maintainable code aligned with team standards and best practices.
• Contribute to the shared component library and design system with reusable components.
• Support code reviews within the team with constructive feedback.
• Participate in incident response and root cause analysis for production issues.
• Be part of the on-call shift.

Conocimientos

React

TypeScript

CSS

Redux Toolkit

Zustand

Web performance

Accessibility (WCAG)

SSR/Next.js

Express.js

Node.js

Websocket

Svelte

Live data apps

CI/CD

English (B2)

Herramientas

Next.js

Express.js

socket.io

Descripción del empleo

Our mission

We are a cutting-edge e-commerce company developing products for our own technological platform. Our creative, smart and dedicated teams pool their knowledge and experience to find the best solutions to meet project needs, while maintaining sustainable and long-lasting results. How? By making sure that our teams thrive and develop professionally. Strong advocates of hiring top talent and letting them do what they do best, we strive to create a workplace that allows for an open, collaborative and respectful culture.

The Role

We are looking for a Senior JavaScript Developer to join our international team to produce scalable software solutions. You’ll be part of a cross-functional team that’s responsible for the full software development life cycle, from conception to deployment. You will be collaborating with the rest of the engineering team to participate in the architecture, design, development, launching and maintenance of our web applications.
To get the most out of this role you should be proactive and keen to get involved. You must be a strong team player with a can-do approach, who can work under minimal supervision. You must also have a great passion for learning and be able to communicate with your colleagues in both Spanish and English.

Key Responsibilities

• Implement scalable, modular, and high‑performance frontend solutions using React, NextJS, AstroJS and TypeScript with modern tooling following team architecture guidelines.
• Build features that handle real‑time data updates, fast user interactions and complex state management, contributing to the team's performance and scalability goals.
• Work closely with product, design, quality and backend teams to deliver features with quality and speed.
• Write clean, maintainable code aligned with team coding standards and best practices.
• Contribute actively to the shared component library and design system, building reusable components consistent with established patterns.
• Support code reviews within the team, providing constructive and actionable feedback.
• Participate in incident response and contribute to root cause analysis for production issues.
• Be part of the on-call shift.

AI-assisted engineering practices

• Identify high-impact areas where AI reduces effort
• Build repeatable prompting workflows for :
  • Generating components aligned with the design system
  • Generating tests from stories/specs
  • Code review preparation
  • Performance analysis of components
• Architectural reasoning (state boundaries, component splitting, folder structure)
• Intelligent debugging (trace render loops, race conditions, stale closures)
• Detecting anti-patterns in PRs before review
• Share effective prompting patterns with the team

Knowledge and skills you need to have

• Solid experience (5+ years) in modern frontend development with React, TypeScript, and CSS.
• Strong understanding of React patterns, hooks, component lifecycle, and rendering behavior.
• Strong knowledge of state management tools (Redux Toolkit, Zustand, or similar), web performance, and testing practices.
• Working knowledge of web standards, accessibility basics (WCAG), and responsive design.
• Familiarity with SSR frameworks such as Next.js.
• Good knowledge for Express.js and node.js
• Websocket knowledge (socket.io)
• Svelte
• Previous experience building live data applications — e.g. financial trading or similar real-time environments.
• Understanding odds updates or real-time event tracking is a big plus.
• Comfortable working with CI/CD pipelines and automated testing practices (unit, integration).
• B2 English level (written and spoken).

Bonus points for the following

• Ability to evaluate AI-generated output for architectural fit and code quality.
• Experience using AI for refactoring, not just code generation.
• Ability to support and guide junior developers on effective AI usage.
• Ability to contribute to team AI coding rules and prompt guidelines to keep generated code aligned with standards.
• Awareness of AI limitations and ability to critically review AI-generated code before integration.