@tunnel/tun

tsx

TypeScript Execute (tsx): Node.js enhanced to run TypeScript & ESM files

Features

• Blazing fast on-demand TypeScript & ESM compilation
• Works in both CommonJS and ESM packages
• Supports next-gen TypeScript extensions (.cts & .mts)
• Hides experimental feature warnings
• TypeScript REPL
• Resolves tsconfig.json paths

[!TIP] Do you need to compile your TypeScript projects? Try pkgroll—the zero-config bundler tsx uses!

pkgroll is a thin layer over Rollup that auto-configures it based on your package.json entry points.

It supports next-gen TS formats, export maps, .d.ts generation, and more!

About

tsx is a CLI command (alternative to node) for seamlessly running TypeScript & ESM in both commonjs & module package types.

This is for you if you ever wanted:

• A command that can just run TypeScript code without dealing with configuration
• Better interoperability in codebases that use ESM and CJS dependencies
• Something really fast it's unnoticeable!

[!TIP] tsx is not just for TypeScript! It also helps Node load module type packages.

If you're getting the following error, give tsx a try!

require('ESM package');
^

Error [ERR_REQUIRE_ESM]: require() of ES Module <ESM package> from ./file.js not supported.
Instead change the require of <ESM package> in ./file.js to a dynamic import() which is available in all CommonJS modules.

Quick start

Try tsx now without setup! Just pass in a TypeScript file:

npx tsx ./script.ts

Mission

1. Enhance Node.js with TypeScript support
2. Improve ESM <-> CJS interoperability as the ecosystem migrates to ESM
3. Support the LTS versions of Node.js

Install

Local installation

If you're using it in an npm project, install it as a development dependency:

npm install --save-dev tsx

Then you can reference it directly in the package.json#scripts object (you don't need npx here):

{
    "scripts": {
        "dev": "tsx ..."
    }
}

To use the binary, you can call it with npx while in the project directory:

npx tsx ...

Global installation

If you want to use it in any arbitrary project without npx, install it globally:

npm install --global tsx

Then, you can call tsx directly:

tsx ...

Usage

tsx is a Node.js wrapper

tsx wraps around Node.js to enhance it with TypeScript support. Because it's a drop-in replacement for node, it supports all Node.js command-line flags.

# --no-warnings is a Node.js flag
tsx --no-warnings ./file.ts

Run TypeScript / ESM / CJS module

Pass in a file to run:

tsx ./file.ts

Custom tsconfig.json path

By default, tsconfig.json will be detected from the current working directory.

To set a custom path, use the --tsconfig flag:

tsx --tsconfig ./path/to/tsconfig.custom.json ./file.ts

Alternatively, use the TSX_TSCONFIG_PATH environment variable:

TSX_TSCONFIG_PATH=./path/to/tsconfig.custom.json tsx ./file.ts

Watch mode

Run file and automatically rerun on changes:

tsx watch ./file.ts

All imported files are watched except from the following directories: node_modules, bower_components, vendor, dist, and .* (hidden directories).

Ignore files from watch

To exclude files from being watched, pass in a path or glob to the --ignore flag:

tsx watch --ignore ./ignore-me.js --ignore ./ignore-me-too.js ./file.ts

Tips

• Press Return to manually rerun
• Pass in --clear-screen=false to disable clearing the screen on rerun

REPL

Start a TypeScript REPL by running with no arguments:

tsx

Cache

Modules transformations are cached in the system cache directory (TMPDIR). Transforms are cached by content hash, so duplicate dependencies are not re-transformed.

Set the --no-cache flag to disable the cache:

tsx --no-cache ./file.ts

Alternatively, use the TSX_DISABLE_CACHE environment variable:

TSX_DISABLE_CACHE=1 tsx ./file.ts

Node.js Loader

tsx is a standalone binary designed to be used in place of node, but sometimes you'll want to use node directly. For example, when adding TypeScript & ESM support to npm-installed binaries.

To use tsx as a Node.js loader, pass it in to the --import flag. This will add TypeScript & ESM support for both Module and CommonJS contexts.

node --import tsx ./file.ts

Or as an environment variable:

NODE_OPTIONS='--import tsx' node ./file.ts

Note: The loader is limited to adding support for loading TypeScript/ESM files. CLI features such as watch mode or suppressing "experimental feature" warnings will not be available.

ESM only loader

If you only need to add TypeScript support in a Module context, you can use the ESM loader:

Node.js v20.6.0 and above

node --import tsx/esm ./file.ts

Node.js v20.5.1 and below

node --loader tsx/esm ./file.ts

CommonJS only loader

If you only need to add TypeScript & ESM support in a CommonJS context, you can use the CJS loader:

node --require tsx/cjs ./file.ts

Hashbang

If you prefer to write scripts that doesn't need to be passed into tsx, you can declare it in the hashbang.

Simply add #!/usr/bin/env tsx at the top of your file:

file.ts

#!/usr/bin/env tsx

console.log('argv:', process.argv.slice(2))

And make the file executable:

chmod +x ./file.ts

Now, you can run the file without passing it into tsx:

$ ./file.ts hello
argv: [ 'hello' ]

VS Code debugging

Setup

Create the following configuration file in your project to setup debugging in VS Code:

.vscode/launch.json

{
    "version": "0.2.0",

    "configurations": [
        /*
        Each config in this array is an option in the debug drop-down
        See below for configurations to add...
        */
    ],
}

Debugging method 1: Run tsx directly from VSCode

1. Add the following configuration to the configurations array in .vscode/launch.json:

   {
       "name": "tsx",
       "type": "node",
       "request": "launch",
   
       // Debug current file in VSCode
       "program": "${file}",
   
       /*
       Path to tsx binary
       Assuming locally installed
       */
       "runtimeExecutable": "${workspaceRoot}/node_modules/.bin/tsx",
   
       /*
       Open terminal when debugging starts (Optional)
       Useful to see console.logs
       */
       "console": "integratedTerminal",
       "internalConsoleOptions": "neverOpen",
   
       // Files to exclude from debugger (e.g. call stack)
       "skipFiles": [
           // Node.js internal core modules
           "<node_internals>/**",
   
           // Ignore all dependencies (optional)
           "${workspaceFolder}/node_modules/**",
       ],
   }

2. In VSCode, open the file you want to run

3. Go to VSCode's debug panel, select "tsx" in the drop down, and hit the play button (F5).

Debugging method 2: Attach to a running Node.js process

This method works for any Node.js process and it's not specific to tsx

1. Add the following configuration to the configurations array in .vscode/launch.json:

   {
       "name": "Attach to process",
       "type": "node",
       "request": "attach",
       "port": 9229,
       "skipFiles": [
           // Node.js internal core modules
           "<node_internals>/**",
   
           // Ignore all dependencies (optional)
           "${workspaceFolder}/node_modules/**",
       ],
   }

2. Run tsx with --inspect-brk in a terminal window:

   tsx --inspect-brk ./your-file.ts 

3. Go to VSCode's debug panel, select "Attach to process" in the drop down, and hit the play button (F5).

See the VSCode documentation on Launch Configuration for more information.

Support

If there's a problem you're encountering or something you need help with, don't hesitate to take advantage of my Priority Support service where you can ask me questions in an exclusive forum. I'm well equppied to assist you with this project and would be happy to help you out! 🙂

FAQ

Why is it named tsx?

tsx stands for "TypeScript execute". Mirroring npx, which stands for "Node.js package execute".

The 3-character package name offers an elegant developer experience, allowing usage like: npx tsx ....

Unfortunately, it overlaps with React's TSX/JSX, which stands for "TypeScript XML".

Does it type check the code it runs?

No. tsx is designed to be a simple TypeScript runner.

If you need type-checking, you can use an IDE like VS Code and it will type-check as you code via IntelliSense. Alternatively, you can run the TypeScript Compiler only for type-checking (e.g. tsc --noEmit) as a linting step.

How is tsx different from ts-node?

They're both tools to run TypeScript files. But tsx does a lot more to improve the experience of using Node.js.

tsx just works. It's zero-config and doesn't require tsconfig.json to get started, making it easy for users that just want to run TypeScript code and not get caught up in the configuration.

It's a single binary with no peer-dependencies (e.g. TypeScript or esbuild), so there is no setup necessary, enabling usage that is elegant and frictionless for first-time users:

npx tsx ./script.ts

tsx is zero-config because it has smart detections built in. As a runtime, it detects what's imported to make many options in tsconfig.json redundant—which was designed for compiling matching files regardless of whether they're imported.

It seamlessly adapts between CommonJS and ESM package types by detecting how modules are loaded (require() or import) to determine how to compile them. It even adds support for require()ing ESM modules from CommonJS so you don't have to worry about your dependencies as the ecosystem migrates to ESM.

Newer and unsupported syntax & features like importing node: prefixes are downgraded by detecting the Node.js version. For large TypeScript codebases, it has tsconfig.json paths aliasing support out of the box.

At the core, tsx is powered by esbuild for blazing fast TypeScript compilation, whereas ts-node (by default) uses the TypeScript compiler. Because esbuild doesn't type check, tsx is similar to ts-node --esm --swc (which uses the SWC compiler).

As a bonus, tsx also comes with a watcher to speed up your development.

Here's an exhaustive technical comparison between tsx, ts-node, and other runtimes.

Does it have a configuration file?

No. tsx's integration with Node.js is designed to be simple & seamless. However, it supports a few properties from tsconfig.json to determine how to compile TypeScript files.

Does it have any limitations?

TypeScript & ESM transformations are handled by esbuild, so it shares the same limitations such as:

• Compatibility with code executed via eval() is not preserved
• Only certain tsconfig.json properties are supported
• emitDecoratorMetadata is not supported

For details, refer to esbuild's JavaScript caveats and TypeScript caveats documentation.

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