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Bun treats TypeScript as a first-class citizen.
## Running `.ts` files
Bun can directly execute `.ts` and `.tsx` files just like vanilla JavaScript, with no extra configuration. If you import a `.ts` or `.tsx` file (or an `npm` module that exports these files), Bun internally transpiles it into JavaScript then executes the file.
**Note** — Similar to other build tools, Bun does not typecheck the files. Use [`tsc`](https://www.typescriptlang.org/docs/handbook/compiler-options.html) (the official TypeScript CLI) if you're looking to catch static type errors.
{% callout %}
**Is transpiling still necessary?** — Because Bun can directly execute TypeScript, you may not need to transpile your TypeScript to run in production. Bun internally transpiles every file it executes (both `.js` and `.ts`), so the additional overhead of directly executing your `.ts/.tsx` source files is negligible.
That said, if you are using Bun as a development tool but still targeting Node.js or browsers in production, you'll still need to transpile.
{% /callout %}
## Configuring `tsconfig.json`
Bun supports a number of features that TypeScript doesn't support by default, such as extensioned imports, top-level await, and `exports` conditions. It also implements global APIs like the `Bun`. To enable these features, your `tsconfig.json` must be configured properly.
{% callout %}
If you initialized your project with `bun init`, everything is already configured properly.
{% /callout %}
To get started, install the `bun-types` package.
```sh
$ bun add -d bun-types # dev dependency
```
If you're using a canary build of Bun, use the `canary` tag. The canary package is updated on every commit to the `main` branch.
```sh
$ bun add -d bun-types@canary
```
<!-- ### Quick setup
{% callout %}
**Note** — This approach requires TypeScript 5.0 or later!
{% /callout %}
Add the following to your `tsconfig.json`.
```json-diff
{
+ "extends": ["bun-types"]
// other options...
}
```
{% callout %}
**Note** — The `"extends"` field in your `tsconfig.json` can accept an array of values. If you're already using `"extends"`, just add `"bun-types"` to the array.
{% /callout %}
That's it! You should be able to use Bun's full feature set without seeing any TypeScript compiler errors.
### Manual setup -->
### Recommended `compilerOptions`
These are the recommended `compilerOptions` for a Bun project.
```jsonc
{
"compilerOptions": {
// add Bun type definitions
"types": ["bun-types"],
// enable latest features
"lib": ["esnext"],
"module": "esnext",
"target": "esnext",
// if TS 5.x+
"moduleResolution": "bundler",
"allowImportingTsExtensions": true,
"moduleDetection": "force",
// if TS 4.x or earlier
"moduleResolution": "nodenext",
"jsx": "react-jsx", // support JSX
"allowJs": true, // allow importing `.js` from `.ts`
"esModuleInterop": true, // allow default imports for CommonJS modules
// best practices
"strict": true,
"forceConsistentCasingInFileNames": true,
"skipLibCheck": true
}
}
```
## Path mapping
When resolving modules, Bun's runtime respects path mappings defined in [`compilerOptions.paths`](https://www.typescriptlang.org/tsconfig#paths) in your `tsconfig.json`. No other runtime does this.
Given the following `tsconfig.json`...
```json
{
"compilerOptions": {
"paths": {
"data": ["./data.ts"]
}
}
}
```
...the import from `"data"` will work as expected.
{% codetabs %}
```ts#index.ts
import { foo } from "data";
console.log(foo); // => "Hello world!"
```
```ts#data.ts
export const foo = "Hello world!"
```
{% /codetabs %}
|
