esjava

library0.0.8jsnpmunverified

ESJava (v0.0.8) is an experimental transpiler that converts Java source code to ES6 (ES2015) JavaScript. It targets ES6 features such as classes, arrow functions, and static getters. Release cadence is low; the project has not seen updates since 2016. Compared to other Java-to-JS tools like GWT or J2CL, ESJava is a lightweight, single-pass transpiler focused on syntactic translation without runtime libraries. It is primarily a proof-of-concept for converting small Java programs, with limited support for Java standard library or advanced language features.

web-framework

npm install esjava

github ↗package ↗

INSTALL

IMPORT

SIG · ESJAVA

esjava

web-frameworkjavascriptv0.0.8

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

esjava

✓ import esjava from 'esjava'

✗ const esjava = require('esjava')

ESJava provides ES modules; CommonJS require is not officially supported and may fail if using the default npm build without transpilation.

compile

✓ import { compile } from 'esjava'

✗ const compile = require('esjava').compile

The named export 'compile' is available in ES module mode only.

Demonstrates converting a simple Java class with a main method to ES6 JavaScript using the compile function.

import { compile } from 'esjava'; const javaCode = ` public class Hello { public static void main(String[] args) { System.out.println("Hello, world!"); } } `; const jsCode = compile(javaCode); console.log(jsCode); // Output: // 'use strict'; // class Hello { // static main(args) { // console.log("Hello, world!"); // } // }

esjava --version

Debug

Known issues

deprecatedPackage has not been updated since 2016 and is effectively abandoned.

fix

Consider using modern alternatives like J2CL or TeaVM for production use.

affects: >=0.0.0

gotchaOnly supports a subset of Java 8 features; many standard library classes (e.g., java.util) are not transpiled and will cause runtime errors.

fix

Avoid using Java standard library classes that are not ES6 equivalents; manually implement or polyfill missing functionality.

affects: <=0.0.8

gotchaStatic final fields are transpiled to ES6 getters, which are read-only but can be overridden in subclasses, differing from Java's final behavior.

fix

Be aware that static final fields are not truly immutable across subclasses; use Object.defineProperty for stricter immutability if needed.

affects: >=0.0.0

deprecatedThe CLI tool uses an older version of commander; command-line usage may not work with recent Node.js versions.

fix

Use the programmatic API (import { compile } from 'esjava') instead of the CLI.

affects: <=0.0.8

Errors

Common errors & fixes

Error: Cannot find module 'esjava'

Package not installed or installed but using CommonJS require with an ESM-only package.

fix

Install the package: npm install esjava. If using require, switch to import or use dynamic import().

SyntaxError: Unexpected token 'export'

Trying to require an ES module with CommonJS require.

fix

Use import instead of require, or set type: module in package.json.

Upgrade

Version history

0.0.8latest on npm

Audit

Dependencies

commanderrequiredused for CLI argument parsing

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/mazko/ESJava ↗

packagehttps://www.npmjs.com/package/esjava ↗