js2il 0.8.23

js2il – JavaScript to .NET IL (consumer guide)

js2il is a .NET global tool that parses JavaScript (ES) and emits ECMA‑335 IL you can run on .NET.

Install

• Prerequisite: .NET 10 SDK or later installed.
• Install the tool globally:

dotnet tool install --global js2il

Update later:

dotnet tool update --global js2il

Uninstall:

dotnet tool uninstall --global js2il

Usage

js2il <InputFile> [<OutputPath>] [options]

Options

• -i, --input The JavaScript file to convert (positional supported)
• -o, --output Output folder for the generated IL/assembly (created if missing; defaults to the input file directory)
• -v, --verbose Print compiler diagnostics to the console
• --diagnostic-file <path> Write compiler diagnostics to a text file
• -a, --analyzeunused Report unused functions/properties/variables --version Show version information and exit

Help: -h, --help, -?

Example:

# Convert tests\simple.js and write output next to the file
js2il .\tests\simple.js

# Convert to a specific directory with verbose output
js2il .\tests\simple.js -o .\out -v

What gets generated?

Given an input like C:\code\sample.js, js2il will emit the following into the output directory (default: alongside the input file):

• sample.dll
  • A .NET assembly (targeting net10.0) containing IL corresponding to your JavaScript.
  • The assembly name is the input file name without extension.
  • Contains a Program.Main entry point that executes your script when run.
• sample.runtimeconfig.json
  • Runtime configuration for the dotnet host (framework: .NET 10).
• JavaScriptRuntime.dll (+ optional JavaScriptRuntime.pdb if available)
  • Required runtime support library that provides JS primitives (e.g., console.log, arrays, objects) used by the emitted IL.
  • This file is copied next to your generated assembly and must be present at runtime.

Run it with:

dotnet .\sample.dll

Notes:

• Console output (e.g., console.log) is implemented via the bundled JavaScriptRuntime.dll.
• This is a prototype and doesn’t yet support all JavaScript features. See the repo docs for supported syntax and feature coverage.
• Errors are written to stderr and known failures return a non-zero exit code.

Limitations

• Target framework: net10.0
• Not all JS features are supported; some constructs may be validated and rejected with explanations.
• Emitted IL and runtime surface are subject to change between previews.

Troubleshooting

• Ensure the .NET 10 SDK/runtime is on PATH: dotnet --info
• Use -v to print diagnostics to the console, or --diagnostic-file <path> to capture diagnostics to a file.
• File an issue with a minimal JS sample if you suspect a bug.

Samples

This package ships a small set of C# hosting samples under samples/.

To validate the samples from the .nupkg:

# Download the package (replace VERSION)
$version = "VERSION"
$url = "https://api.nuget.org/v3-flatcontainer/js2il/$version/js2il.$version.nupkg"
Invoke-WebRequest -Uri $url -OutFile "js2il.$version.nupkg"

# Extract it (a .nupkg is a zip; Expand-Archive expects a .zip extension)
Copy-Item "js2il.$version.nupkg" "js2il.$version.zip" -Force
Expand-Archive -Path "js2il.$version.zip" -DestinationPath "js2il_pkg" -Force

# Build + run a sample
dotnet build .\js2il_pkg\samples\Hosting.Basic\host
dotnet run --project .\js2il_pkg\samples\Hosting.Basic\host

Links

• Source, issues, docs: https://github.com/tomacox74/js2il
• License: Apache-2.0