Overrides whose parameters widen and whose results convert into the
inherited ones keep the inherited slot, which converts around the
override's own body; Error values take code writes, `in` tests and
Object.assign; and a few gaps behind generic wrappers close:
- Method overrides: each inherited argument converts into the
override's parameter (equal, wider, or a checked extraction from an
`any` slot) and the override's result converts into the inherited one
(narrower, a convertible union, a widening Promise payload, anything
convertible over an `any` base). The slot %C.m keeps the inherited
ABI and forwards to %C.m$own; TypeScript callers typed with the
subclass call $own directly when nothing overrides below. Async
overrides of sync and async bases, and JavaScript overrides of
builtin or TypeScript bases (zod's ZodError.toString) are included;
a toString slot converts its result with ToString.
- `err.code = value` on Error values in TypeScript: strings set the
runtime code slot (and the error's checked-dynamic node, if any); other
values clear it and keep the dynamic own property.
- `'key' in err` with any receiver: declared members answer true;
otherwise a class test over the declaring subclasses, a runtime lookup
of the error's own properties, or an Object.prototype member.
- `Object.assign(err, ...sources)` onto an Error target copies onto the
error, re-reads name, message, stack, cause and code into the typed
slots, and returns the error.
- `Error & { ... }` intersections whose extra members have checkable
types are Error values; those members read and write the error's own
properties, each read checked at its declared type.
- Catch bindings typed `any` read as checked-dynamic values (member
reads and writes, assertions); a multi-statement type guard with an
`unknown` parameter takes the caught value as an ordinary argument;
Error members of a binding narrowed to an Error-extending interface
read through the same value.
- Lambda parameters typed `any` by their default are checked-dynamic
slots; forwarded-only rest tuples with optional positions forward
their slots; `value as never` from an untyped value into a typed
parameter takes the checked extraction to the parameter's type.
- Lexical `this` stops at generic instance frames, so an instance no
longer sees the receiver of the caller that triggered it. The fence
for `this` captured through a plain function now points at the
`this` keyword.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
scriptc
scriptc compiles TypeScript and JavaScript to native executables and WebAssembly. It uses the types checked by the TypeScript compiler to generate machine code, and the output runs without Node.js installed. npm packages your program imports compile along with it. Code scriptc can't compile is reported at build time with a diagnostic and, where available, a rewrite hint.
scriptc is experimental and supports a subset of JavaScript, TypeScript, and Node.js APIs. Run scriptc coverage on an existing program to see how much of it compiles, and see the limitations and Node.js compatibility reference for details.
Installation
Install with Node.js 24 or later and npm:
$ npm install -g scriptc
The installed compiler runs natively on macOS, Linux, and Windows. Node.js is needed only to install it and to run WASI modules with scriptc run. Standalone compiler archives are also available from GitHub Releases.
Building executables requires a linker and the platform SDK or sysroot. See the quickstart for prerequisites and platform support for host requirements, cross-compilation, and WebAssembly.
Build a program
Create hello.ts:
const who = process.argv.length > 2 ? process.argv[2] : "world";
console.log(`hello, ${who}`);
scriptc run compiles the file and runs the result:
$ scriptc run hello.ts
hello, world
scriptc build writes an executable:
$ scriptc build hello.ts -o hello >/dev/null
$ ./hello scriptc
hello, scriptc
These examples use POSIX shell syntax. On Windows, build hello.exe and run it with .\hello.exe.
Use scriptc coverage hello.ts to check what compiles before you build. See coverage reports for details.
Use Node APIs
Supported Node APIs compile to the native runtime. For example, server.ts:
import { createServer } from "node:http";
const server = createServer((req, res) => {
res.setHeader("content-type", "application/json");
res.end(JSON.stringify({ path: req.url }));
});
server.listen(8080, () => {
console.log("listening on http://localhost:8080");
});
$ scriptc build server.ts -o server >/dev/null
$ ./server
listening on http://localhost:8080
Use npm packages
npm packages compile into the executable with your code, so it doesn't read node_modules at runtime.
Create cli.ts:
import pc from "picocolors";
console.log(pc.green("hello from scriptc"));
$ npm install picocolors
$ scriptc build cli.ts -o cli >/dev/null
$ ./cli
hello from scriptc
Package support is partial. See npm dependencies for which packages compile and how to check them.
Documentation
- Introduction: what scriptc is and what you can build.
- Quickstart: installation and your first executable.
- Coverage reports: check whether an existing program compiles.
- Platform support: cross-compilation and WebAssembly.
- CLI reference: commands, options, and output formats.
- Native program objects: use compiler output in external builds.
- Native FFI: call C ABI functions from compiled programs.
- WebAssembly modules: build and embed WASI modules.
- Examples: programs and integration examples in this repository.
Contributing
See CONTRIBUTING.md for source setup, testing, native artifact builds, and docs development.