OXC Transformer

The OXC transformer is built on the next-generation, Rust-based oxc toolchain. It aims to be one of the fastest JavaScript/TypeScript transformers available.

Overview

This example shows how to select the OXC transformer. OXC compilation is driven almost entirely by your tsconfig.json and the build runtime — Packem derives the TypeScript and JSX settings for you, so there is very little to configure by hand.

OXC handles:

• TypeScript transformation (type stripping, down-leveling to a resolved target)
• JSX (classic and automatic runtimes)
• Source maps

When to Use

• Experimental projects willing to adopt bleeding-edge tooling
• Performance research and benchmarking
• Contributing to or evaluating the next generation of JavaScript tooling

For production libraries, prefer esbuild or swc, which are stable and feature-complete.

Project Setup

TypeScript Configuration

OXC reads JSX and target settings from your tsconfig. A typical setup:

{
  "compilerOptions": {
    "target": "ES2020",
    "jsx": "react-jsx",
    "jsxImportSource": "react"
  }
}

Packem Configuration

Selecting the transformer is all that most projects need — the JSX runtime, pragma, and TypeScript options are resolved from your tsconfig automatically:

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/oxc'

export default defineConfig({
  transformer
})

Building

packem build

Notes

• OXC's target is resolved from your tsconfig compilerOptions.target plus the build runtime, the same way esbuild's target is resolved.
• JSX refresh (React Fast Refresh) is disabled — it is not needed for a library build.
• Declaration files are generated by Packem's dedicated declaration plugin, not by OXC.
• Because OXC is experimental, validate your output carefully and consider falling back to esbuild or swc if you hit transformation issues.