Senior Developer, Front End

Critical Mass is looking for a talented and motivated Senior Front-End Developer to join our technology team, responsible for delivering innovative, visually compelling, and high-performance web experiences using modern JavaScript technologies. This is a unique opportunity to work with a high-profile client, collaborating closely with design, UX, and engineering teams to create best in class digital communications and interactive experiences.

Please note this is a hybrid, contract position.

You will:

• Collaborate with designers and UX specialists to rapidly prototype and implement engaging user interactions
• Lead development using Vanilla JavaScript (no frameworks) and modern frontend standards
• Build and maintain components using technologies like React, Vue, and jQuery—all implemented in native JavaScript for optimal performance and extensibility
• Develop visually rich, interactive 3D animations utilizing WebGL and Three.js
• Create high impact web animations and transitions using GSAP/GreenSock
• Integrate dynamic content from JSON or markdown sources using Handlebars (HBS) templating
• Write modular, maintainable styles with SASS, leveraging its advanced capabilities for scalable CSS architecture
• Ensure cross device and cross browser compatibility, accessibility (WCAG), and optimal page performance.
• Mentor junior frontend developers and contribute to code reviews, documentation, and testing best practices.

You have:

• 5+ years of professional experience building consumer facing websites with advanced skills in Vanilla JavaScript
• Deep understanding of HTML5 with at least 5 years of experience
• Advanced expertise in CSS3, with a strong focus on styling, layout, and design
• Proficient in SASS for writing modular, maintainable, and scalable stylesheets
• Strong command of responsive design principles to ensure seamless experiences across all devices
• Proven expertise with GSAP/GreenSock or similar animation libraries to deliver smooth, high quality web animations
• Experience building interactive graphics or 3D web experiences using WebGL and Three.js
• Hands on experience with Handlebars (HBS) for dynamic templating, including ingestion of JSON and markdown sources
• Familiarity with React, Vue, and jQuery, including implementing these patterns with Vanilla JS
• Strong Git proficiency and experience with modern development workflows (CI/CD, terminal, etc.)
• Solid troubleshooting and performance optimization skills
• Strong communication skills and ability to work collaboratively in a distributed team environment
• Experience working with enterprise level CSS systems or custom extensible design languages
• Knowledge of web accessibility standards (WCAG) and best practices
• Familiarity with content management systems (CMS), such as Adobe Experience Manager (AEM), or API driven architectures
• Experience with build tools like Webpack and task runners

Bonus if you have:

• Experience with advanced CSS methodologies or custom extensible style languages
• Demonstrated ability to push the boundaries of web technology with innovative UI/UX
• Familiarity with content management systems (CMS), such as Adobe Experience Manager (AEM), or API driven architectures
• Agency experience

What We Offer:

• Global maternity and parental leave
• Competitive benefits packages
• Vacation, compassionate leave, sick days, and flex days
• Access to online services for families and new parents
• Diversity and Inclusion Board with 12 affinity groups
• Internal learning and development programs
• Enterprise-wide employee discounts