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Job Description

Core JavaScript / TypeScript Engineer - London - Hybrid

£150,000 – £200,000 + pension, private healthcare, gym membership, hardware budget

London (Hybrid – 2 days WFH)

A high-growth software company is building the next of high-performance UI frameworks and data-intensive visualisation technology. Their products power mission-critical applications used by global enterprises, financial institutions, and technology firms, relied on every day by millions of users worldwide.

They hire engineers who enjoy working close to the metal of the browser, solving problems that demand a deep understanding of algorithms, runtime behaviour, and performance at scale.

This is not typical web development. It’s engineering at the limits of what modern browsers can do.

What you’ll work on

Design and optimise the core runtime of a high-performance UI framework used globally in real-time environments. Push the boundaries of JavaScript, TypeScript, and the browser rendering pipeline to deliver smooth performance on massive datasets. Solve complex engineering challenges around tree structures, recursion, memory allocation, rendering performance, and data-flow architecture. Own features end-to-end, design, build, test, document, and release. Contribute to libraries used by developers and enterprise engineering teams worldwide.

What you’ll bring

Deep, practical mastery of vanilla JavaScript and TypeScript. Strong exposure to C++, Java, or C#, with a systems-level mindset. A solid understanding of data structures, algorithms, and performance optimisation. Experience building complex, highly scalable systems — not just CRUD interfaces. Familiarity with frameworks such as React, Angular, or Vue, and a strong grasp of how they interact with the DOM. Ability to diagnose bottlenecks, eliminate memory leaks, and optimise rendering and throughput. An appreciation for clean software design, correctness, and maintainability.

Why this role matters

You’ll work on core engineering problems that most developers never get close to. You’ll join a team of deeply experienced engineers with backgrounds across low-level and large-scale systems. You’ll operate in a fast, engineering-led culture with minimal bureaucracy and high autonomy. You’ll enjoy a top-tier package, including: £150,000–£200,000 salary Private healthcare Pension Gym membership 25 days holiday + bank holidays High-end hardware budget Central London office with two days WFH each week.

If you want to engineer the foundations behind some of the world’s most demanding applications, this is the environment built for you. Get in touch!

If you are interested in applying for this job please press the Apply Button and follow the application process. Energy Jobline wishes you the very best of luck in your next career move.