An "OS for your browser" that breaks the browser language barrier (includes a plugin-free JVM).
TypeScript Java JavaScript

doppio: A JVM in TypeScript v0.4.2

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doppio is a double shot of espresso. In this case it's also a JVM written in TypeScript and an active research project of the PLASMA group at the University of Massachusetts.

To try doppio now, head to the live demo page.

To learn more, read some documentation, or read our academic paper (alt. link w/ no paywall) published at PLDI 2014!

You can also get in touch via our mailing list or via the IRC channel #plasma-umass on Freenode.

Getting & Building the Code

Before attempting to build doppio, you must have the following installed:

  • Node v4.0 or higher
  • NPM package grunt-cli installed globally
    • npm install -g grunt-cli
  • Java 8 JDK

If you are on Windows, you will need the following installed:

  • Git (must be on your PATH)
  • Python (must be on your PATH)
  • A version of Visual Studio

Run the following commands to build doppio. Note that your first time building may take some time, as the build script will download the entire Java Class Library.

git clone
cd doppio
npm install
grunt release      # For browser integration.
grunt release-cli  # For command-line use.


Run the full test suite using node.js:

grunt test

Run the full test suite in a web browser:

grunt test-browser

Run a specific test by invoking the test runner manually:

node build/dev-cli/console/test_runner.js classes/test/Strings

Command-line Usage

Run doppio with node.js (after grunt release-cli):

./doppio classes.demo.Fib 7
./doppio -jar my_application.jar
./doppio -cp my/class/path SomeClass

Integrating Into Your Site

Check out our Developer Guide for information on how you can integrate doppio into your website!

You can also build and interact with a simple example application with:

grunt examples

The code is in docs/examples.