`s.charAt(i) === "c"`, and `s[i] === "c"` where the index is proven in bounds, built a one-character string to compare with the literal. When the literal is one UTF-16 code unit, the comparison now reads `s.charCodeAt(i)` and compares the number. charCodeAt converts the index the same way charAt does, and an index out of range answers NaN, which equals no unit, as "" equals no one-unit literal. A switch on `s.charAt(i)` whose case tests are all one-unit literals switches on the code unit the same way. A switch on a `string | undefined` value with string literal cases, such as an array element or an optional field, lowered to a chain of union equalities. It now tests for undefined, which matches no case, and dispatches the string through the string switch: by byte length, then by the literal's leading bytes. `String.fromCharCode(a, b, ...)` with up to sixteen arguments passes the codes to the runtime in a stack array instead of a heap f64[], and up to 64 code units encode into a stack buffer instead of a heap scratch block. `.length` of a string that is not ASCII counts its UTF-16 units. The string index keeps four entries, so a program that read the lengths of more long texts than that in turn (the text of every source file) walked each whole string on every read. Lengths of non-ASCII strings longer than 64 bytes now go into a 1024-slot table keyed by address, allocated by the first length it records. A slot is dropped when the string is freed or reallocated and when an append changes it in place, which is where the index drops its facts.
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.