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Julien Lange

Senior JavaScript Developer Web Components, Design System & Fullstack

I build Web interfaces that stand the test of time. During 5 years at Fnac Darty, I learned that a good component isn't one that works — it's one that three different teams can use without calling you.

Île-de-France · Available

Julien Lange, senior JavaScript developer freelance
01

Experience

Fnac Darty

Freelance

Senior Front-End Developer

Octobre 2021Juillet 2026Ivry-sur-Seine

Long-term mission on fnac.com, France's leading e-commerce site, on the most visited pages: product pages, homepage, sub-homes, search results (~100,000 views/day on search results, ~50,000 on homepage). Stack: ASP.NET/Razor + JavaScript ES6+/Web Components on-prem, progressive migration to a cloud Azure architecture (server-side micro-frontends).

~100k
views / day
search results
~50k
views / day
homepage
~50
editors
SMILE users
8
markets
FR, BE, CH, ES, PT…
  • Internal Web Components Library

    Creation and maintenance of an internal NPM library of 20 to 30 UI components in native Custom Elements, consumed by 3 front-end teams. Migration from a proprietary component architecture to the native Web Components spec. Creation of shared packages (SCSS design tokens, common ESLint/Babel configs) — the foundation of a Design System.

    Web ComponentsCustom ElementsNPMDesign TokensSCSSESLint
  • Cloud Migration (M2C)

    Migration of Home/Sub-home layers to a server-side MFE framework (UI fragments, Razor tag helpers, Kafka/Cosmos DB pipeline), migration of Liquid templates to CSHTML, CSS Less → SCSS migration.

    Micro-frontendsAzureRazor/CSHTMLKafkaCosmos DBSCSS
  • SMILE CMS Redesign

    Autonomous Figma mockup design and complete technical front-end overhaul, deployed in production and used by ~50 editors across 8 markets (FR, BE-FR, BE-NL, CH-FR, CH-DE, ES, PT, Fnac Pro).

    FigmaCMSJavaScript8 marchés50 éditeurs
  • Kamino — Ad Integration

    Integration of 7 on-site ad formats (video, display, native) desktop/mobile, with complete analytics tracking.

    JavaScriptPublicité displayAnalyticsResponsive
  • Arrow — Marketplace Seller

    Front-end integration of marketplace seller information across all surfaces: product pages, listings, mini-product page, buybox.

    JavaScriptWeb ComponentsMarketplaceRazor
  • Other projects

    DSA compliance, WebPerf optimization (Core Web Vitals), technical SEO, product page redesign from 2 to 3 columns.

    WebPerfCore Web VitalsSEODSAA/B Testing

42 Lisboa

CDI

System Engineer & Pedagogical Supervisor

Septembre 2020Juillet 2021Lisbonne, Portugal

Recruited as an alumnus for the opening of the 42 school campus in Lisbon. Hybrid role: technical infrastructure and pedagogy. Fully English-speaking work environment.

Julien Lange supervising a piscine at 42 Lisboa — students on iMacs in the open space
42 Lisboa, 2020 — supervising a piscine
  • Infrastructure & DevOps

    Setting up the infrastructure (VMware, Ansible): exams, automated grading system, LDAP sessions on iMacs. Service maintenance, incident resolution for student sessions.

    VMwareAnsibleLDAPLinuxDevOps
  • Next.js E-commerce Site

    Development of an e-commerce site for the school's merchandising: product catalog, OAuth authentication via the official 42 API, order management.

    Next.jsOAuthAPI 42E-commerceNode.js
  • Pedagogy

    Pedagogical role during school 'piscines': code review of C projects, student mentoring.

    CCode ReviewPédagogieÉcole 42

X-FAB

Freelance

C Developer, Industrial Systems

Mars 2020Septembre 2020Ormoy

C development of a communication program with industrial machines via the SECS/GEM standard (semiconductor industry), triggering actions and retrieving production data.

X-FAB clean room — engineers in sterile suits in front of semiconductor manufacturing equipment
X-FAB manufacturing environment — semiconductor industry
  • SECS/GEM Communication

    Implementation of a SECS/GEM-compliant communication program to control and query semiconductor manufacturing equipment.

    CSECS/GEMSystèmes industrielsSemi-conducteurs

Société Générale

Stage

JS/Python Developer, Innovation Lab

Avril 2018Novembre 2018Paris

Development of the web interface and use cases for the Pepper robot (Softbank Robotics), deployed in production in bank branches. Development of microservices for the Cognitive Services project.

  • Pepper Robot (Softbank Robotics)

    Web interface and use cases for the Pepper conversational robot, deployed in production in Société Générale branches.

    JavaScript ES6PythonReactReduxWebpackDocker
  • Microservices — Cognitive Services

    Development of REST microservices for the Cognitive Services artificial intelligence project.

    PythonDockerSwaggerMicroservicesREST API
02

Skills

255075100Front-endFrameworksBuildArchitectureBack-endCloud & InfraMethods

Front-end

95%
  • JavaScript ES6+
  • Web Components / Custom Elements
  • HTML5
  • SCSS
  • Less
  • CSHTML / Razor (.NET MVC)

Frameworks

90%
  • React
  • Next.js
  • Redux

Build & Tooling

78%
  • Webpack
  • Babel
  • NPM
  • ESLint
  • PostCSS
  • Prettier

Architecture

85%
  • Micro-frontends (MFE)
  • Design Systems
  • Web Components natifs
  • Design Tokens

Back-end & Languages

62%
  • Node.js
  • Python
  • C#
  • .NET
  • C

Cloud & Infra

68%
  • Microsoft Azure
  • VMware
  • Ansible
  • Docker
  • Kafka
  • Cosmos DB

Tools & Methods

80%
  • Figma
  • Datadog
  • Git
  • Jira
  • Agile / Scrum
  • WCAG / RGAA
  • SEO technique
03

Key Projects

Fnac Darty

SMILE — Internal CMS Redesign

Autonomous Figma mockup design and complete technical front-end overhaul of an internal CMS. Deployed in production and used daily by ~50 content editors across 8 markets (France, Belgium, Switzerland, Spain, Portugal, Fnac Pro).

FigmaJavaScriptWeb ComponentsCMS8 marchés
Fnac Darty

Web Components Library / Design System

Creation and maintenance of an internal NPM library of 20 to 30 UI components in native Custom Elements, consumed by 3 front-end teams on fnac.com. Shared packages (SCSS design tokens, common ESLint/Babel configs) forming the foundation of a Design System.

Web ComponentsCustom ElementsNPMDesign TokensSCSSESLint
42 Lisboa

Next.js E-commerce — 42 Lisboa

Merchandising site for 42 Lisboa school: product catalog, OAuth authentication via the official 42 API, order management. Built independently from scratch, deployed in production.

Next.jsTypeScriptOAuthAPI 42E-commerceNode.js
Société Générale

Pepper Robot — Web Interface

Web interface and use cases for the Pepper conversational robot by Softbank Robotics, developed within Société Générale's Innovation Lab and deployed in production in bank branches.

ReactReduxJavaScript ES6PythonDockerWebpack
04

Education

Degrees

École 42

2016 — 2019

Information Technology Architect

Intensive project-based learning and peer review. C, C++, Shell scripting, algorithms, Unix, networking, systems. No lectures — 100% hands-on and collaborative.

Lycée Rosa Parks

2016

STI2D Baccalaureate

Science and Technology of Industry and Sustainable Development, specializing in computing and digital technology.

Continuing education & certifications

Mars 2025

Web Accessibility (WCAG / RGAA)

Fnac Darty — Formation interne

Training on WCAG 2.1 and RGAA 4.1 standards: accessibility criteria, screen reader testing, technical audits.

Juin 2025

AI & GitHub Copilot

Fnac Darty — Formation interne

Using generative AI in development workflows: GitHub Copilot, prompt engineering, best practices.

2022

Microsoft Azure Cloud

Fnac Darty — Formation interne

Azure fundamentals: cloud services, distributed architecture, Cosmos DB, Kafka, application deployment.

2022

Design Thinker

Formation externe

Design Thinking methodology: empathy, ideation, prototyping, user testing. Applied to concrete projects.

05

Contact

Available for freelance missions in Île-de-France or fully remote. Feel free to reach out to discuss a project or opportunity.

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Or directly by email