typescript.md

To install the TypeScript definitions for Bun's built-in APIs, install bun-types.

$ bun add -d bun-types # dev dependency

Then include "bun-types" in the compilerOptions.types in your tsconfig.json:

  {
    "compilerOptions": {
+     "types": ["bun-types"]
    }
  }

At this point, you should be able to reference the Bun global in your TypeScript files without seeing errors in your editor.

console.log(Bun.version);

Suggested compilerOptions

Bun supports things like top-level await, JSX, and extensioned .ts imports, which TypeScript doesn't allow by default. Below is a set of recommended compilerOptions for a Bun project, so you can use these features without seeing compiler warnings from TypeScript.

{
  "compilerOptions": {
    // add Bun type definitions
    "types": ["bun-types"],

    // enable latest features
    "lib": ["ESNext"],
    "module": "esnext",
    "target": "esnext",

    // if TS 5.x+
    "moduleResolution": "bundler",
    "noEmit": true,
    "allowImportingTsExtensions": true,
    "moduleDetection": "force",
    // if TS 4.x or earlier
    // "moduleResolution": "nodenext",

    "jsx": "react-jsx", // support JSX
    "allowJs": true, // allow importing `.js` from `.ts`

    // best practices
    "strict": true,
    "forceConsistentCasingInFileNames": true,
    "skipLibCheck": true,
    "composite": true,
    "downlevelIteration": true,
    "allowSyntheticDefaultImports": true
  }
}

If you run bun init in a new directory, this tsconfig.json will be generated for you.

$ bun init

DOM types

Unfortunately, setting a value for "types" means that TypeScript will ignore other global type definitions, including lib: ["dom"]. If you need to add DOM types into your project, add the following triple-slash directives at the top of any TypeScript file in your project.

/// <reference lib="dom" />
/// <reference lib="dom.iterable" />