`JSON.parse(text) as T`, `const x: T = anyValue` and `await res.json() as T` threw `TypeError: expected X at $.path, got Y` when the value did not fit `T`. Node never checks an assertion and continues with the value it has, so the build-container listener rejected an order Node accepts and a JWT with a string `exp` became a 500. A failed cast now keeps its value when it initializes a `const`/`let` binding declared in a function or block and only the code after the cast reads the binding. That code (the statements after the cast in each enclosing statement list, up to the declaration) lowers twice: the static copy, unchanged, runs while the value fits; a dynamic copy, in which the binding and everything derived from it is typed `any`, runs after a failure, so missing members read undefined, wrong-typed members keep their values, extra members stay visible in source order, and objects keep their identity. The cast sets the flag that selects the copy: the fused JSON.parse helper's slow path and the plain check call scr_dyn_check_recover, which takes back the TypeError and parks the value for checkedCast.fallbackTaken/fallbackTake. A failed value that flows into a typed slot outside the region is checked there, as any `any` value is: it continues when it fits and throws at that use when it does not. A statement of the dynamic copy with no `any` lowering becomes a runtime fence that throws only when a failed value reaches it. Module-level bindings, regions with hoisted declarations or super() calls, union targets and targets holding class instances, and --tier=static-only (and library mode) keep the throwing cast. `a?.b.c` on an `any` value now short-circuits only on `a`, so `.c` throws when `a.b` is undefined, as in Node. 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.