Typescript-support NPM

typescript-support

This package installs a require extension, adding support for running .ts and .tsx files directly.

Features:

Full syntactic and semantic type checking.
Loads configuration from the closest tsconfig.json, with support for multiple configurations inside a project.
Built-in support for source-maps, powered by source-map-support.
Node 8+ friendly defaults, for basic transpilation when no tsconfig.json is found.

Getting started

Install the library as a dev dependency in an existing TypeScript project:

yarn add typescript-support --dev

Usage with Node.js:

node -r typescript-support ./my-script.ts

Usage with Mocha:

mocha -r typescript-support "./test/**/*.unit.ts?(x)" --watch-extensions ts,tsx

Usage with Visual Studio Code:

// in .vscode/launch.json, under "configurations"
{
    "type": "node",
    "request": "launch",
    "name": "Launch Program",
    "runtimeArgs": [
        "-r",
        "typescript-support"
    ],
    "args": [
        "${workspaceFolder}/src/my-script.ts"
    ]
}

If throwing on type errors is too invasive to your development process, you can use an alternative entry point that calls console.warn() instead:

node -r typescript-support/warn ./my-script.ts

Why?

I recently experimented with a neat project setup where I have one tsconfig.json in my src folder, and a second tsconfig.json in my test folder.

Each config created a different type environment by explicitly specifying which @types packages are included (via compilerOptions->types).

So while my tests had access to @types/mocha and its globals, my src folder knew nothing of describe() and it().

The above setup gave me type isolation between folders sharing the same node_modules.

For better development velocity, I quickly wanted a TypeScript Node.js integration that supports this setup, and would give me proper type checking per environment. This led to this library.

How?

For each .ts or .tsx file, the extension finds the closest tsconfig.json. For each config, it instantiates a separate TypeScript Language Service and uses that service to transpile and type-check the file.

tsconfig.json lookup is done once per directory (cached for the second lookup in that directory). There is one Language Service per tsconfig.json, and all running services share a document registry.

If no tsconfig.json is found for a typescript file, this integration transpiles it directly using the Node 8+ friendly compiler options.

Similar projects

ts-node - a much more complete solution. It includes a ts-node cli/repl, and require hook registration. It does not support multiple tsconfigs out of the box, afaik.