Features

• Run TypeScript files directly
  • Uses Node's experimental module loader
• Build to pure ES Module output
  • Fast (6ms to build this tool, minified and DCE'd)
  • Pure, spec-compliant ESM output
• Supports node <file> usage
• Supports ESM --loader usage

Requirements

Because TSM packages are pure ESM environments, only Node 16+ is supported.

Usage

tsm can be used to run TypeScript directly, and the CLI can be used to build your project to fully-resolved ESM.

Install tsm in your project (or globally) to run or build your module:

yarn add @tsmodule/tsm

Building TypeScript modules

You can build your TypeScript module to ESM with the build CLI command:

tsm build

Source will be compiled from src/ to dist/ and will contain only ESM-compliant import specifiers as resolved by the tsm loader. This ESM output will not contain incomplete specifiers like ./path/to/module (no file extension) and can be executed directly via node dist/index.js.

Executing TypeScript directly

Provided they're executable (via chmod +x file.ts), TypeScript files can be executed directly (via ./index.ts) with the #!/usr/bin/env tsm shebang present:

#!/usr/bin/env tsm

const test: string = "hello world"
console.log(test);

Shell:

$ ./file.ts

# hello world

Advanced usage

# use as `node` replacement
$ tsm server.ts

# forwards any `node` ENV or flags
$ NO_COLOR=1 tsm server.ts --trace-warnings

# use as `--require` hook
$ node --require @tsmodule/tsm server.tsx
$ node -r @tsmodule/tsm server.tsx

# use as `--loader` hook
$ node --loader @tsmodule/tsm main.jsx

How it works

tsm is effectively a proxy for node --loader @tsmodule/tsm [...]. The tsm loader allows ES module resolution to natively import from specifiers like ./thing -> ./thing.ts, and uses esbuild to load TypeScript on-the-fly.

For module builds, the TypeScript Compiler API is used to resolve incomplete specifiers in emitted esbuild output and transform them into complete ESM-compliant specifiers (i.e. ./path/to/file.js).

Module configuration

All packages built with tsm build are ES modules. They should have "type": "module" set in package.json and can use the exports field to resolve conditional exports.

tsm build forces the following tsconfig.json values:

{
  "rootDir": "src/",
  "outDir": "dist/",
}

By default, package.json will be configured like so:

{
  "files": ["dist/"],
  "exports": {
    "./package.json": "./package.json",
    "./": "./dist/index.js",
    "./*": "./dist/*/index.js"
  },
}

Such that "index modules" at e.g. src/test/index.ts will be available at my-package/test. This has no restriction on internal imports between files, only the default configuration for how downstream consumers can import from module subpaths.

Footnotes

• const x = require(...) statements in imported modules will be forward-polyfilled to backwards-compatible const { default: x } = await import(...) statements by the loader.

  This has no runtime effect, and is simply a way to support legacy CJS require statements by transforming them into equivalent dynamic ESM imports.

License

MIT © C. Lewis, Luke Edwards