The minimalist TypeScript script runner for NodeJS.

• On-demand TypeScript transpilation so fast you won't even notice.
• Supports source maps for accurate stack traces.
• Does not spawn another process to transpile TypeScript.
• Does not spawn another Node process to run your script.
• Strictly follows modern Node semantics for ESM and CommonJS modules.
• Zero config: no config file, no command line arguments, no environment variables, no nothing.
• Does not even need a tsconfig.json.
• Light: only 220 kilobytes installed!
• Zero dependency!

• Not for running full-blown TypeScript projects.
• No REPL support.

ts-run is a CLI command that you can use to run TypeScript scripts in NodeJS as if they were written in plain JavaScript. It is a simple as:

ts-run ./some-script.ts

The idea is that you take advantage of your IntelliSense-compatible editor to author your scripts with full type checking on, and ts-run will transparently run them without you having to run the TypeScript compliler beforehand.

ts-run requires a modern (as of january 2024) version of NodeJS:

• Node 18 version 18.19.0 or later
• Node 20 version 20.6.0 or later
• Any version >= 21

For everyday use, you may want to install ts-run globally:

npm install -g @septh/ts-run

and have it always available in your CLI:

ts-run path/to/some/script.ts

Or you may install it locally in a project:

npm install --save-dev @septh/ts-run

and then call it from the scripts section in package.json:

{
    "scripts": {
        "get-data": "ts-run ./scripts/download-data.ts",
        "release": "ts-run ./scripts/prepare-release.ts"
    }
}

or from the command line:

npx ts-run ./scripts/do-something.ts

ts-run's sole role is to transpile TypeScript code to JavaScript code, no more, no less. It does not try to optimize or minify your code and it does not downlevel nor polyfill JavaScript. Therefore, there are a few things you should keep in mind while authoring your scripts.

Beginning with ts-run 1.2.6, .js specifiers are supported to import .ts scripts:

// a.ts
export const something = 'great'

// b.ts
import { something } from './a.js'  // works!

But you may also use .ts specifiers:

// b.ts
import { something } from './a.ts'  // works too!

Whatever your choice, remember that extensions are mandatory in ESM scripts.

In short:

1. The import ... from 'specifier' syntax is left as is in ES modules and transformed to const ... = require('specifier') in CommonJS modules.
2. The import namespace = require('specifier') syntax is valid in ES modules only and is transformed to const require = createRequire(); const namespace = require('specifier'), with the createRequire() call being hoisted if used several times.
3. Dynamics imports are always left untouched.
4. exports are transformed to module.exports assignments in CommonJS modules.
5. Type-only imports and exports, whether explicit or implicit, are recognized and silently removed.

TypeScript's module resolution specificities are not handled; instead, Node's module resolution algorithm is always used. In other words, as far as ts-run is concerned, it is like if both module and moduleResolution were always set to Node16, and paths was not set.

ts-run uses a customized build of Sucrase under the hood and therefore exhibits the same potential bugs and misbehaviors than Sucrase.

If ts-run seems to not work as you'd expect, you should first check if this there is a Sucrase issue open for your problem. If not, please file an issue on ts-run.

As stated earlier, ts-run does not need (and in fact, does not even look for) a tsconfig.json file. The same is not true however for the TypeScript Language Server that your IntelliSense-aware editor relies on. You'll find the following tsconfig.json useful to get the right warnings and errors reports in your IDE:

{
  "compilerOptions": {
    // This tells the TypeScript language server that this directory contains Node scripts.
    "module": "Node16",

    // For scripts that use .ts import specifiers.
    // Please note that `noEmit` is required when using `allowImportingTsExtensions`
    "allowImportingTsExtensions": true,
    "noEmit": true,

    // Scripts are transpiled in isolation; this imposes a few restrictions
    // on some TypeScript features like const enums or namespaces.
    // (see https://www.typescriptlang.org/tsconfig#isolatedModules)
    "isolatedModules": true,

    // Of course, add any other type-checking options you deem necessary:
    "strict": true
    // etc.
  }
}

For reference, you can find such a tsconfig.json file in the test folder of this repository.

I have tested ts-run with ava and Node itself and it works very well in both cases. I can see no reason why it wouldn't work with another test-runner.

This very repo is using Node as its test-runner of choice. Here's what your scripts section in package.json may look like:

  "scripts": {
    "test": "node --import=@septh/ts-run --test test/**/*.test.{ts,mts,cts}"
  }

Note: to pass command line options to Node itself, you need to use the --import syntax as shown above.

Add the following entry to your package.json:

  "ava": {
    "extensions": {
      "ts": "module",
      "mts": "module",
      "cts": "commonjs"
    },
    "nodeArguments": [
      "--import=@septh/ts-run"
    ]
  }

Here's an example: https://github.com/Septh/rollup-plugin-node-externals

Any test-runner that provides a mean to specify Node arguments (just like ava above) should work happily with ts-run.

In the worst case, you can always use the NODE_OPTIONS environment variable:

NODE_OPTIONS="--import=@septh/ts-run" my-test-runner

Because ts-run generates sourcemaps, you can set breakpoints in your script, inspect variables, etc.

Either run ts-run in the VS Code Javascript Debug Terminal or use the following launch.json configuration (replace <path-to-your-script.ts> with the actual path to your script):

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Run with ts-run",
            "request": "launch",
            "type": "node",
            "runtimeArgs": [
                "--import=@septh/ts-run"
            ],
            "program": "${workspaceFolder}/<path-to-your-script.ts>",
            "windows": {
                "program": "${workspaceFolder}\\<path-to-your-script.ts>"
            },
            "skipFiles": [
                "<node_internals>/**",
                "**/node_modules/**"
            ],
            "resolveSourceMapLocations": [
                "!**/node_modules/**"
            ],
        }
    ]
}

MIT.