Senior JavaScript / TypeScript Developer

Cornspring
London
1 month ago
Applications closed

Related Jobs

View all jobs

AWS Backend Engineer (Inside IR35)

Senior Python Developer

Principal Data Scientist

Data Scientist, AI/ML, Associate

Machine Learning Engineer, London

Senior MLops (Full Stack) Engineer | London | Foundation Models in London - SoCode Recruitment

Job Title:Senior JavaScript / TypeScript Developer – UI (AI Interfaces) & Excel Add-in

Location:London - (Hybrid)

Type:Full-time


About Us:Cornspring is a dynamic start-up developing Family Office services through a unique combination of innovative technology and data management excellence. Our platform leverages state-of-the-art generative AI and large language models to provide unparalleled insights and efficiency to Family Office investment and accounting data.


We pride ourselves on fostering a collaborative and inclusive work environment where we prize creativity, excellence in engineering, a powerful customer focus and attention to problem-solving through great design.


Job Description:

We are seeking an experienced Front-end Developer to join our team, focusing on building our Excel Add-in solutions and web portal platform. You will be responsible for developing sophisticated data manipulation interfaces using TypeScript within the Microsoft Office Add-in ecosystem while also creating intuitive web applications where clients interact with their data using AI. This role requires deep understanding of data visualization, REST API integration, and responsive design principles. You will work closely with our back-end team to ensure seamless integration with our AWS services while delivering exceptional user experiences in both Excel and our React-based web portal.


The Role

We’re looking for a Senior JavaScript / TypeScript Developer who thrives at the intersection of elegant UI development and advanced Excel Add-in engineering. You’ll lead development on two core user-facing components:

  1. Our AI-driven web platform, built using JavaScript, React and TypeScript
  2. Our Excel Add-in, deployed internally within Microsoft 365, integrating directly with our platform APIs

This role is perfect for someone who enjoys building robust user experiences that bridge traditional productivity tools (like Excel) with modern, responsive web apps—and who is excited by the opportunity to work with AI and financial data.


Key Responsibilities

  • Design, build, and maintain high-performance Excel Add-ins using TypeScript and Office.js, tailored for internal Microsoft 365 deployment
  • Develop and scale web interfaces our AI solutions, data visualization, and reporting
  • Collaborate with backend engineers to connect APIs, manage state, and streamline data integration
  • Ensure excellent UX in both browser and Excel environments, with intuitive, performant, and consistent interfaces
  • Contribute to architectural decisions, component libraries, and development best practices
  • Support cross-team coordination around security, testing, deployment, and CI/CD pipelines


What We're Looking For

  • Professional front-end development experience with JavaScript, React and TypeScript
  • Strong expertise in modern UI development practices
  • Proven experience building and deploying Office Add-ins, especially within Microsoft 365 for internal enterprise use
  • Deep knowledge of the Excel JavaScript API, object models, and data handling within workbook constraints
  • Comfortable integrating with REST APIs, handling authentication flows (e.g., OAuth), and managing async data interactions
  • Strong understanding of front-end performance optimization, state management, and cross-environment compatibility
  • Experience working in Agile teams, with a proactive and ownership-driven mindset


Bonus Points For

  • Experience with data-intensive applications or financial tools
  • Familiarity with data visualization libraries (e.g., D3.js, Chart.js, Recharts)
  • Knowledge of Microsoft Graph API and M365 deployment configurations
  • Exposure to AWS services (Lambda, API Gateway, Cognito, etc.)
  • Understanding of AI and LLM patterns for chat, collaboration or search interfaces


What We Offer

  • Work with cutting-edge AI and data technologies.
  • Collaborate with a small, high-calibre, mission-driven team
  • Opportunities for professional growth and development.
  • Flexible work hours and remote work options.
  • Engaging and challenging projects that make a real impact to our sector.
  • Fast-paced, deeply impactful work with real users and rapid iterations


Important Application Criteria

To ensure we make the best use of your time and ours, please review the following before submitting your application.

This role is suited to candidates who:

  • Are based in the UK and able to work effectively with a London-based team
  • Have the unrestricted right to work in the UK –note that we are currently not able to offer visa sponsorship
  • Bring proven experience in both modern UI development and Excel Add-in engineering in data-centric or enterprise environments
  • Operate confidently at a senior level, capable of contributing to architectural decisions and working autonomously in a fast-moving setting
  • Candidates passing initial review will be asked to undertake a skills assessment

We value thoughtful, relevant applications and will prioritise those that clearly align with the requirements outlined above.

If this sounds like the right fit for your background and ambitions, we’d be delighted to hear from you.


How to Apply

Send us your CV and (optionally) GitHub/portfolio, along with a short note on your experience with Excel Add-ins, UI development, and what excites you about this role.

Get the latest insights and jobs direct. Sign up for our newsletter.

By subscribing you agree to our privacy policy and terms of service.

Industry Insights

Discover insightful articles, industry insights, expert tips, and curated resources.

Jobs

Portfolio Projects That Get You Hired for AI Jobs (With Real GitHub Examples)

In the fast-evolving world of artificial intelligence (AI), an impressive portfolio of projects can act as your passport to landing a sought-after role. Even if you’ve aced interviews in the past, employers in AI and machine learning (ML) are increasingly asking candidates to demonstrate hands-on experience through the projects they’ve built and shared online. This is because practical ability often speaks volumes about your suitability for a role—far more than any exam or certification alone could. In this article, we’ll explore how to build an outstanding AI portfolio that catches the eye of recruiters and hiring managers, including: Why an AI portfolio is crucial for job seekers. How to choose AI projects that align with your target roles. Specific project ideas and real GitHub examples to help you stand out. Best practices for showcasing your work, from writing clear READMEs to using Jupyter notebooks effectively. Tips on structuring your GitHub so that employers can instantly see your value. Moreover, we’ll discuss how you can use your portfolio to connect with top employers in AI, with a handy link to our CV-upload page on Artificial Intelligence Jobs for when you’re ready to apply. By the end, you’ll have a clear roadmap to building a portfolio that will help secure interviews—and the AI job—of your dreams.

Jobs Careers

AI Job Interview Warm‑Up: 30 Real Coding & System‑Design Questions

In today's competitive AI job market, nailing a technical interview can be the difference between landing your dream role and getting lost in the crowd. Whether you're looking to break into machine learning, deep learning, NLP (Natural Language Processing), or data science, your problem-solving skills and system design expertise are certain to be put to the test. AI‑related job interviews typically involve a range of coding challenges, algorithmic puzzles, and system design questions. You’ll often be asked to delve into the principles of machine learning pipelines, discuss how to optimise large-scale systems, and demonstrate your coding proficiency in languages like Python, C++, or Java. Adequate preparation not only boosts your confidence but also reduces the likelihood of fumbling through unfamiliar territory. If you’re actively seeking positions at major tech companies or innovative AI start-ups, then check out www.artificialintelligencejobs.co.uk for some of the latest vacancies in the UK. Meanwhile, this blog post will guide you through 30 real coding & system-design questions you’re likely to encounter during your AI job interview. This list is designed to help you practise, anticipate typical question patterns, and stay ahead of the competition. By reading through each question and thinking about the possible approaches, you’ll sharpen your problem-solving skills, time management, and critical thinking. Each question covers fundamental concepts that employers regularly test, ensuring you’re well-equipped for success. Let’s dive right in.

Jobs

Negotiating Your AI Job Offer: Equity, Bonuses & Perks Explained

Artificial intelligence (AI) has proven itself to be one of the most transformative forces in today’s business world. From smart chatbots in customer service to predictive analytics in finance, AI technologies are reshaping how organisations operate and innovate. As the demand for AI professionals grows, so does the complexity of compensation packages. If you’re a mid‑senior AI professional, you’ve likely seen job offers that include far more than just a base salary—think equity, bonuses, and a range of perks designed to entice you into joining or staying with a company. For many, the focus remains squarely on salary. While that’s understandable—after all, your monthly take‑home pay is what covers day-to-day expenses—limiting your negotiations to salary alone can leave considerable value on the table. From stock options in ambitious startups to sign‑on bonuses that ‘buy you out’ of your current contract, modern AI job offers often include elements that can significantly boost your long-term wealth and job satisfaction. This article aims to shed light on the full scope of AI compensation—specifically focusing on how equity, bonuses, and perks can enhance (or sometimes detract from) the overall value of your package. We’ll delve into how these elements work in practice, what to watch out for, and how to navigate the negotiation process effectively. Our goal is to provide mid‑senior AI professionals with the insights and tools to land a holistic compensation deal that accurately reflects their technical expertise, leadership potential, and strategic importance in this fast-moving field. Whether you’re eyeing a leadership role in machine learning at an established tech giant, or you’re considering a pioneering position at a disruptive AI startup, the knowledge in this guide will help you weigh the merits of base salary alongside the potential riches—and risks—of equity, bonuses, and other benefits. By the end, you’ll have a clearer sense of how to align your compensation with both your immediate lifestyle needs and long-term career aspirations.

🍪 We use cookies to enhance your browsing experience on our website. By continuing to use this site, you consent to the use of cookies as described in our Cookie Policy. You can review our Cookie Policy for more information.