❄️ Elsa is a minimal, fast and secure runtime for JavaScript and TypeScript written in Go



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Elsa is a minimal, fast and secure runtime for JavaScript and TypeScript written in Go, leveraging the power from QuickJS.


  • URL based imports.
  • No fs, net access unless specified.
  • Compliant to web standards.
  • Supports TypeScript.
  • Module caching.
  • Bundle your script into a single file.
  • Create a standalone executable for your bundles.


Not yet released, build from source instead.

Build from source

You will need Go installed on your machine before building.

Install go-bindata using go get github.com/go-bindata/go-bindata/...

Clone the repo on your $GOPATH and run make build to trigger the build process.

Getting Started

Try running a simple program:

// hello.ts
import { hello } from "https://x.nest.land/[email protected]/mod.ts";

> elsa run hello.ts
Hello, Elsa


Start by creating an issue about your feature or bug! Then, create a PR and we'll land it 😄



Where to use Elsa and where not to...

Elsa is small and embeddable into Go programs, using Quickjs as the backend comes with certain pros and cons -


  • Suitable for CLI applications and shipping them as an executable
  • Native bindings to system level APIs (webview, etc)
  • Hosting discord bots on your raspberry pie 😉
  • Embeddable inside your Go programs.
  • General purpose scripting


  • Slower runtime execution than Node and Deno
  • Slower backends
  • Double GC

Why choose QuickJS over V8?

QuickJS is a small and embeddable JavaScript engine but it lacks V8's JIT for fast JavaScript execution. Although, it doesn't mean you cannot use Elsa on backends and CPU intensive tasks.

QuickJS has a better startup time than V8 so it would be a strong alternative for CLI apps and short-lived runs.

Looks like a QuickJS wrapper to me?

Technically, Node and Deno are also V8 wrappers. All do the same job, init engine - init ops - bundle - run. Most people don't realise that implementing native ops is what makes a runtime and not an interpreter.

What's the status of the project?

It is in it's very early stages of development i.e. nothing should be considered stable. Feel free to take it for a spin though :)

What does "minimal" actually refer to?

The goal is to fullfil the bare minimum requirements needed for development of a project. Elsa, although aims to be extendable via plugins. A few examples of features that are not likely to be included in Elsa are tools for formatting, linting and analysis.

In short, develop - package - ship


Elsa.land is licensed under MIT License.

  • Implement filesystem ops

    Implement filesystem ops

    The goal right now is to implement all the file system APIs provided by Deno - https://github.com/denoland/deno/blob/master/cli/ops/fs.rs

    There is already a Elsa.readFile binding in core/dispatch.go with it's corresponding js call at js/01_namespace.js.

    Looking forward to recieve PRs :smile:

    enhancement good first issue 
    opened by littledivy 5
  • Fix some code quality issues and add code transformer

    Fix some code quality issues and add code transformer

    Fixes #85

    This pull request fixes some of the issues raised by DeepSource on my fork of this repo.

    Some issues were automatically fixed by DeepSource, while I fixed some of them by hand.

    This PR also contains a .deepsource.toml, in case you want to run continuous quality analyses on your repository. If you wish to do so, you can follow these steps:

    • Merge this PR.
    • Signup on DeepSource here.
    • Activate analysis on your repo here.

    Adding to reporting the code quality issues, I have also added the Go (gofmt) and JavaScript (Prettier) Transformers which support auto-formatting of code on every new pull-request. You can find the transformers docs here.

    If you don't want to use DeepSource, I can edit the PR to remove the .deepsource.toml file.

    opened by siddhant-deepsource 4
  • Project revival and long-term goals

    Project revival and long-term goals

    Hey everyone :wave:
    Been busy with several other projects recently which made it hard for me and @filipporeds to be able to work full-time on this.

    It's time to resume work on elsa:

    1. Revive PRs
    2. Embedding friendly
    3. Adapt internal workings from Deno (resource tables, json_ops, etc). (:heart: Deno)
    4. Fix bundle issues
    5. Runtime backends (Switch backends from quickjs, ducktape, v8, etc)

    Elsa as an embedded runtime is a major goal. Certain applications include k8 using elsa for built-in typescript support, etc.

    Contributions and feature requests are accepted in the issue tracker. Feel free to hop on the discord server.

    opened by littledivy 3
  • Comparison with Deno

    Comparison with Deno

    Hello, the project looks really cool, looking forward to the http API!

    However, I'd like to suggest to add a comparison table with Deno, e.g. perf, features, size comparison.

    I've seen Deno vs Elsa benchmarks, but a comparison table (either in readme or separate file) with feature lists would be cool as well :D

    opened by talentlessguy 3
  • elsa/quickjs should fork bellard/quickjs

    elsa/quickjs should fork bellard/quickjs

    elsa/quickjs forks lithdew/quickjs:


    But it's not an official repository and its owner is not an author.

    Recently the author of quickjs created their account at GitHub and hosted quickjs repository:


    It's official and maintained. I strongly recommend elsa to fork the official repository.

    opened by rhysd 2
  • there is already an open source project called Elsa

    there is already an open source project called Elsa

    Scott McPeak's C++ front-end is called elsa: http://dsw.users.sonic.net/oink/elsa_features.html

    This is not an obscure project: it was used by Mozilla to do source-to-source transforms on C++, the first time that had been done in history, as it preceded Clang/LLVM.

    opened by dsw 1
  • Ineffectual sync.WaitGroup in ops.Serve

    Ineffectual sync.WaitGroup in ops.Serve

    https://github.com/elsaland/elsa/blob/0819922b24f01849de855ff2852f2f28631fc1cb/core/ops/serve.go#L66 This call to wg.Wait is unreachable because the for loop preceding it never breaks. As a fix, a chan error should be used instead of a sync.WaitGroup so the error from http.ListenAndServe can be returned as well (see #75.)

    opened by samhza 1
  • feat(fmt/colors)


    a while ago I made a small color library per terminal for dart based on ANSI, I think it can be implemented within the color library, this is the repo of my implementation

    enhancement std 
    opened by buttercubz 1
  • Can I interact with a JS script while it is running?

    Can I interact with a JS script while it is running?

    For example, I have a javascript game loop, I use a Go grpc server to run it.

    When the player sends an operation request, the Go grpc server will change the status of javascript game loop.

    Can I do it with elsa?

    opened by HZHgagaga 0
  • Downloadable binary anywhere

    Downloadable binary anywhere

    Hi there,

    Is there downloadable binary anywhere of elsa, or do I need to compile it myself?

    I can see this step in the github actions to generate and upload a binary, but it wasn't obvious to me where I might try to download a binary for linux or OS X:

       - name: Upload Elsa executables
            uses: actions/[email protected]
              name: elsa-${{ matrix.os }}
              path: ./src/github.com/elsaland/elsa/elsa-${{ matrix.os }}

    I'm not a confident go programmer, so there might be something really obvious I'm missing, and I'm happy to update the README once I know the answer.

    opened by mrchrisadams 1
  • GO interop

    GO interop

    Is there a way to use this library akin to how something like Goja or Otto usage looks like? I'm working on a CLI where I want to have a JS runtime that will run perhaps many scripts (both files and from variables in go) in the same context. Right now I'm using Otto, and it works, but I'd like something that supports ES6 (especially modules). Here's an example of what I'm doing to setup a vm:

    vm := otto.New()
    err = vm.Set("someFunc", func(call otto.FunctionCall) otto.Value {
        message := call.Argument(0).String()
        // some go code here
        return otto.Value{}
    _, err := vm.Run(` // some setup scripts `);

    Then later I have some user-defined scripts I want to execute against that vm (via the Run method), using some of those pre-defined setup/functions and interop as necessary. It doesn't look like this is something Elsa currently can handle, but is this a direction you're going in? If not I have some other options, just none as attractive as what you're doing here I think.

    Thanks in advance, and best of luck!

    opened by davesheldon 1
  • Add tests to `testing/`  and `std/` with Elsa.tests

    Add tests to `testing/` and `std/` with Elsa.tests

    Add tests for all the js/ts files inside testing/ and std/

    The test file should be named in the pattern *_test.js for elsa to identify it as a test file.


    // some_test.js
    import { eq } from "./utils.ts";
      "test mode == `test`": function () {
        eq(Elsa.mode, "test");

    and run ./elsa test

    Marking as a good first issue as anyone with Deno.test experience can give it a try :smile:

    good first issue priority 
    opened by littledivy 2
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