React Developer

November 4, 2025

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Job Description

Haystack is working with Capgemini on this opportunity!

Hybrid, London

Description

We’re hiring a React JS Developer on behalf of Capgemini, a global leader in digital transformation, technology, and engineering services.

You’ll join a collaborative product engineering team building scalable, high-performance web applications for some of the world’s leading organisations. This is a hands-on development role focused on modern JavaScript frameworks, performance optimisation, and clean, accessible code.

What you’ll do

  • Build and maintain responsive, high-quality user interfaces using React JS, JavaScript, HTML5, and CSS3
  • Apply CSS preprocessors such as SASS or LESS to streamline styling and performance
  • Integrate RESTful APIs and manage asynchronous data flows with AJAX and JSON
  • Collaborate closely with cross-functional teams to deliver seamless front-end integrations
  • Ensure accessibility and WCAG/ARIA compliance across all interfaces
  • Write automated unit tests and follow TDD best practices for maintainable code
  • Use Git (and other SCM tools) for version control and collaborative development
  • Leverage build and quality tools such as npm, Grunt/Gulp, and SonarQube
  • Optimise load times and network performance for smoother user experiences

What you’ll bring

  • Strong experience with React JS, JavaScript (ES6+), HTML5, and CSS3
  • Understanding of Node.js and modern JavaScript frameworks
  • Experience using SASS/LESS and front-end build pipelines
  • Familiarity with RESTful APIs, AJAX, and JSON
  • Working knowledge of accessibility standards (WCAG, ARIA)
  • Experience writing unit tests and using TDD approaches
  • Version control experience with Git and build automation tools
  • Attention to detail, collaboration mindset, and a passion for clean, performant code

Why join Capgemini

  • Work with cutting-edge technology across global clients and industries
  • Hybrid flexibility with a collaborative, growth-focused culture
  • Comprehensive benefits and professional development support
  • Opportunity to contribute to digital and sustainable transformation projects at scale