karate-js

A lightweight JavaScript engine implemented in Java from scratch, designed to run on the JVM with full support for concurrent thread execution.

See also: docs.karatelabs.io | docs/DESIGN.md | karate-core

Features

Thread-safe - Full support for concurrent execution across threads
Minimal - small JAR footprint; SLF4J and JSON-smart are the only dependencies
Java Interop - bridge Java and JS code; full control, behavior customization, introspection from Java
Simple - concise codebase, plenty of unit tests
Fast - see benchmarks for numbers

Architecture

Package	Description
`io.karatelabs.js`	Core JavaScript engine (interpreter, runtime, built-in types)
`io.karatelabs.parser`	Parsing infrastructure (lexer, parser, AST nodes) shared with karate-core
`io.karatelabs.common`	Shared utilities (file, OS, string operations)

The engine targets idiomatic ES6 used in real-world JavaScript; some advanced features are intentionally not supported. See docs/DESIGN.md for the JS engine reference.

Usage

java

import io.karatelabs.js.Engine;

Engine engine = new Engine();
Object result = engine.eval("1 + 2");
// result = 3

Java Interop

java

Map<String, Object> context = new HashMap<>();
context.put("greeting", "Hello");

Engine engine = new Engine();
engine.putAll(context);
Object result = engine.eval("greeting + ' World'");
// result = "Hello World"

Third-Party Usage

This module can be used independently of karate-core. If you're integrating karate-js into your own project:

xml

<dependency>
    <groupId>io.karatelabs</groupId>
    <artifactId>karate-js</artifactId>
    <version>2.0.0.RC1</version>
</dependency>

Contributions that improve decoupling for third-party usage are welcome.

License

MIT License