Introduction

CKB-VM is a virtual machine based on the RISC-V instruction set that executes on-chain script on CKB, providing developers with maximum flexibility and power while maintaining security and performance. This approach allows for seamless integration of new cryptographic primitives without hard forks and supports development in any programming language that can target RISC-V, enabling developers to use familiar tools and existing libraries rather than building everything from scratch.

Currently, the main languages used for on-chain script development are C and Rust. While C is accessible to learn, it lacks high-level abstractions, making it challenging to write code that is free from undefined behaviors and security vulnerabilities. Rust offers stronger safety guarantees and modern language features, but its steep learning curve limits widespread adoption among developers.

With the project ckb-js-vm, we aim to enable on-chain script development using TypeScript, one of the world's most popular programming languages. This approach significantly lowers the barrier to entry for blockchain developers, allowing them to leverage the vast JavaScript/TypeScript ecosystem, including its rich libraries, tools, and community support. By providing a unified language for both development and testing, ckb-js-vm creates a streamlined, one-stop solution that eliminates context-switching between languages and accelerates the development cycle for CKB on-chain script programming.

Early Attempt

In the early years, we demonstrated the possibility of using JavaScript on CKB-VM through Duktape, a compact JavaScript engine with readable code and comprehensive documentation. However, this approach suffered from significant performance limitations, with on-chain scripts consuming between 100-1000 M cycles, making it impractical for production environments. These early experiments, while promising conceptually, highlighted the need for a more efficient JavaScript execution solution.

QuickJS, A Fast JavaScript Engine

QuickJS is a lightweight JavaScript engine developed by legendary programmer Fabrice Bellard. It provides impressive performance without relying on JIT compilation, making it ideal for CKB-VM which implements W^X security features that prevent JIT-based optimizations. With QuickJS, we've achieved a significant performance breakthrough, reducing execution costs to under 50M cycles for typical JavaScript operations—a dramatic improvement over previous approaches.

CKB imposes a 500KB size limitation for binaries deployed to a single cell, making QuickJS's focus on code size efficiency particularly valuable for on-chain scripts. QuickJS places a strong emphasis on minimizing code size. For instance, the manual states:

  • The complete regular expression library requires only ~15 KiB (x86 code), excluding Unicode support
  • The full Unicode library adds approximately 45 KiB (x86 code)

Total Solution

With a JavaScript engine, it is still very difficult to develop a full featured on-chain script. We also provide following tools and libraries:

  • libraries in TypeScript
  • building tools
  • framework for unit tests We will introduce these features later.

Comprehensive Development Ecosystem

While integrating a JavaScript engine is a significant advancement, developing production-ready on-chain scripts requires a complete ecosystem of tools and libraries. The ckb-js-vm project delivers a comprehensive solution that includes:

  • A rich set of TypeScript libraries providing CKB-specific abstractions
  • Streamlined build tooling that optimizes code size and performance
  • A robust testing framework enabling comprehensive unit testing
  • Scaffold tools that generate project templates and boilerplate code for rapid development

This end-to-end approach ensures developers can focus on writing business logic rather than wrestling with infrastructure concerns. The subsequent sections of this documentation will explore each component of this ecosystem in detail, demonstrating how they work together to create a seamless development experience.