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README.md

Bun TypeScript type definitions

These are the type definitions for Bun's JavaScript runtime APIs.

Installation

Install the bun-types npm package:

# yarn/npm/pnpm work too, "bun-types" is an ordinary npm package
bun add bun-types

Usage

Add this to your tsconfig.json or jsconfig.json:

{
  "compilerOptions": {
    "lib": ["ESNext"],
    "module": "esnext",
    "target": "esnext",
    // "bun-types" is the important part
    "types": ["bun-types"]
  }
}

Contributing

bun-types is generated via ./bundle.ts.

Adding a new file

1. Add it to ./index.d.ts

How to generate types.d.ts

./bundle.ts merges the types in this folder into a single file.

To run it:

bun generate

Generated docs

bun-types / Exports

bun-types

Table of contents

Namespaces

• "bun"
• "bun:ffi"
• "bun:jsc"
• "bun:sqlite"
• "bun:test"
• "node:path/posix"
• "node:path/win32"
• "node:sys"
• "path/posix"
• "path/win32"
• "supports-color"
• "sys"
• "test"
• HTMLRewriterTypes

Interfaces

• AbortSignalEventMap
• AddEventListenerOptions
• BlobInterface
• BlobPropertyBag
• BufferConstructor
• BufferEncodingOption
• ByteLengthQueuingStrategy
• CloseEvent
• CloseEventInit
• CountQueuingStrategy
• Crypto
• Dict
• DirectUnderlyingSource
• EncodeIntoResult
• ErrnoException
• ErrorEvent
• ErrorEventInit
• Event
• EventInit
• EventListener
• EventListenerObject
• EventListenerOptions
• EventMap
• EventModifierInit
• EventSourceInit
• EventTarget
• FetchEvent
• GenericTransformStream
• Headers
• MessageEvent
• MessageEventInit
• Process
• QueuingStrategy
• QueuingStrategyInit
• QueuingStrategySize
• ReadOnlyDict
• ReadWriteStream
• ReadableStream
• ReadableStreamDefaultController
• ReadableStreamDefaultReadDoneResult
• ReadableStreamDefaultReadValueResult
• ReadableStreamDefaultReader
• ReadableStreamDirectController
• ReadableStreamGenericReader
• ReadableWritablePair
• RequestInit
• ResponseInit
• StreamPipeOptions
• StructuredSerializeOptions
• TransformStream
• TransformStreamDefaultController
• Transformer
• TransformerFlushCallback
• TransformerStartCallback
• TransformerTransformCallback
• UIEventInit
• UnderlyingSink
• UnderlyingSinkAbortCallback
• UnderlyingSinkCloseCallback
• UnderlyingSinkStartCallback
• UnderlyingSinkWriteCallback
• UnderlyingSource
• UnderlyingSourceCancelCallback
• UnderlyingSourcePullCallback
• UnderlyingSourceStartCallback
• VoidFunction
• WebSocket
• WebSocketEventMap
• WritableStream
• WritableStreamDefaultController
• WritableStreamDefaultWriter

Variables

• Bun
• ByteLengthQueuingStrategy
• CloseEvent
• CountQueuingStrategy
• ErrorEvent
• Event
• EventTarget
• Headers
• Loader
• MessageEvent
• ReadableStream
• ReadableStreamDefaultController
• ReadableStreamDefaultReader
• TransformStream
• TransformStreamDefaultController
• WebSocket
• WritableStream
• WritableStreamDefaultController
• WritableStreamDefaultWriter
• crypto
• performance

Functions

• addEventListener
• alert
• atob
• btoa
• confirm
• fetch
• prompt
• removeEventListener
• reportError

Variables

Bun

• Bun: "bun"

Defined in

bun.d.ts:1233

dist/types.d.ts:14263

---

ByteLengthQueuingStrategy

• ByteLengthQueuingStrategy: Object

Type declaration

Name	Type
prototype	ByteLengthQueuingStrategy

Defined in

globals.d.ts:1715

globals.d.ts:1720

dist/types.d.ts:2126

dist/types.d.ts:2131

---

CloseEvent

• CloseEvent: Object

Type declaration

Name	Type
prototype	CloseEvent

Defined in

globals.d.ts:1301

globals.d.ts:1310

dist/types.d.ts:1712

dist/types.d.ts:1721

---

CountQueuingStrategy

• CountQueuingStrategy: Object

Type declaration

Name	Type
prototype	CountQueuingStrategy

Defined in

globals.d.ts:1951

globals.d.ts:1956

dist/types.d.ts:2362

dist/types.d.ts:2367

---

ErrorEvent

• ErrorEvent: Object

Type declaration

Name	Type
prototype	ErrorEvent

Defined in

globals.d.ts:1287

globals.d.ts:1295

dist/types.d.ts:1698

dist/types.d.ts:1706

---

Event

• Event: Object

Type declaration

Name	Type
AT_TARGET	number
BUBBLING_PHASE	number
CAPTURING_PHASE	number
NONE	number
prototype	Event

Defined in

globals.d.ts:1177

globals.d.ts:1275

dist/types.d.ts:1588

dist/types.d.ts:1686

---

EventTarget

• EventTarget: Object

Type declaration

Name	Type
prototype	EventTarget

Defined in

globals.d.ts:1125

globals.d.ts:1171

dist/types.d.ts:1536

dist/types.d.ts:1582

---

Headers

• Headers: Object

Type declaration

Name	Type
prototype	Headers

Defined in

globals.d.ts:271

globals.d.ts:286

dist/types.d.ts:682

dist/types.d.ts:697

---

Loader

• Loader: Object

Low-level JavaScriptCore API for accessing the native ES Module loader (not a Bun API)

Before using this, be aware of a few things:

Using this incorrectly will crash your application.

This API may change any time JavaScriptCore is updated.

Bun may rewrite ESM import specifiers to point to bundled code. This will be confusing when using this API, as it will return a string like "/node_modules.server.bun".

Bun may inject additional imports into your code. This usually has a bun: prefix.

Type declaration

Name	Type	Description
dependencyKeysIfEvaluated	(specifier: string) => string[]	For an already-evaluated module, return the dependencies as module specifiers This list is already sorted and uniqued. Example For this code: js // /foo.js import classNames from 'classnames'; import React from 'react'; import {createElement} from 'react'; This would return: js Loader.dependencyKeysIfEvaluated("/foo.js") ["bun:wrap", "/path/to/node_modules/classnames/index.js", "/path/to/node_modules/react/index.js"]
registry	Map<string, { dependencies: string[] ; module: any ; state: number }>	ESM module registry This lets you implement live reload in Bun. If you delete a module specifier from this map, the next time it's imported, it will be re-transpiled and loaded again. The keys are the module specifiers and the values are metadata about the module. The keys are an implementation detail for Bun that will change between versions. - Userland modules are an absolute file path - Virtual modules have a bun: prefix or node: prefix - JS polyfills start with "/bun-vfs/". "buffer" is an example of a JS polyfill - If you have a node_modules.bun file, many modules will point to that file Virtual modules and JS polyfills are embedded in bun's binary. They don't point to anywhere in your local filesystem.
resolve	(specifier: string) => Promise<string>	The function JavaScriptCore internally calls when you use an import statement. This may return a path to node_modules.server.bun, which will be confusing. Consider Bun.resolve or ImportMeta.resolve instead.
resolveSync	(specifier: string, from: string) => string	Synchronously resolve a module specifier This may return a path to node_modules.server.bun, which will be confusing. Consider Bun.resolveSync instead.

Defined in

globals.d.ts:1583

dist/types.d.ts:1994

---

MessageEvent

• MessageEvent: Object

Type declaration

Name	Type
prototype	MessageEvent<any>

Defined in

globals.d.ts:1316

globals.d.ts:1336

dist/types.d.ts:1727

dist/types.d.ts:1747

---

ReadableStream

• ReadableStream: Object

Type declaration

Name	Type
prototype	ReadableStream<any>

Defined in

globals.d.ts:1673

globals.d.ts:1692

dist/types.d.ts:2084

dist/types.d.ts:2103

---

ReadableStreamDefaultController

• ReadableStreamDefaultController: Object

Type declaration

Name	Type
prototype	ReadableStreamDefaultController<any>

Defined in

globals.d.ts:1725

globals.d.ts:1740

dist/types.d.ts:2136

dist/types.d.ts:2151

---

ReadableStreamDefaultReader

• ReadableStreamDefaultReader: Object

Type declaration

Name	Type
prototype	ReadableStreamDefaultReader<any>

Defined in

globals.d.ts:1745

globals.d.ts:1751

dist/types.d.ts:2156

dist/types.d.ts:2162

---

TransformStream

• TransformStream: Object

Type declaration

Name	Type
prototype	TransformStream<any, any>

Defined in

globals.d.ts:1900

globals.d.ts:1905

dist/types.d.ts:2311

dist/types.d.ts:2316

---

TransformStreamDefaultController

• TransformStreamDefaultController: Object

Type declaration

Name	Type
prototype	TransformStreamDefaultController<any>

Defined in

globals.d.ts:1914

globals.d.ts:1921

dist/types.d.ts:2325

dist/types.d.ts:2332

---

WebSocket

• WebSocket: Object

Type declaration

Name	Type
CLOSED	number
CLOSING	number
CONNECTING	number
OPEN	number
prototype	WebSocket

Defined in

globals.d.ts:1352

globals.d.ts:1407

dist/types.d.ts:1763

dist/types.d.ts:1818

---

WritableStream

• WritableStream: Object

Type declaration

Name	Type
prototype	WritableStream<any>

Defined in

globals.d.ts:1782

globals.d.ts:1789

dist/types.d.ts:2193

dist/types.d.ts:2200

---

WritableStreamDefaultController

• WritableStreamDefaultController: Object

Type declaration

Name	Type
prototype	WritableStreamDefaultController

Defined in

globals.d.ts:1798

globals.d.ts:1802

dist/types.d.ts:2209

dist/types.d.ts:2213

---

WritableStreamDefaultWriter

• WritableStreamDefaultWriter: Object

Type declaration

Name	Type
prototype	WritableStreamDefaultWriter<any>

Defined in

globals.d.ts:1808

globals.d.ts:1818

dist/types.d.ts:2219

dist/types.d.ts:2229

---

crypto

• crypto: Crypto

Defined in

globals.d.ts:754

dist/types.d.ts:1165

---

performance

• performance: Object

Type declaration

Name	Type
now	() => number

Defined in

globals.d.ts:952

dist/types.d.ts:1363

Functions

addEventListener

▸ addEventListener<K>(type, listener, options?): void

Type parameters

Name	Type
K	extends "fetch"

Parameters

Name	Type
type	K
listener	(this: object, ev: EventMap[K]) => any
options?	boolean | AddEventListenerOptions

Returns

void

Defined in

globals.d.ts:1028

▸ addEventListener(type, listener, options?): void

Parameters

Name	Type
type	string
listener	EventListenerOrEventListenerObject
options?	boolean | AddEventListenerOptions

Returns

void

Defined in

globals.d.ts:1033

▸ addEventListener<K>(type, listener, options?): void

Type parameters

Name	Type
K	extends "fetch"

Parameters

Name	Type
type	K
listener	(this: object, ev: EventMap[K]) => any
options?	boolean | AddEventListenerOptions

Returns

void

Defined in

dist/types.d.ts:1439

▸ addEventListener(type, listener, options?): void

Parameters

Name	Type
type	string
listener	EventListenerOrEventListenerObject
options?	boolean | AddEventListenerOptions

Returns

void

Defined in

dist/types.d.ts:1444

---

alert

▸ alert(message?): void

Parameters

Name	Type
message?	string

Returns

void

Defined in

globals.d.ts:1988

▸ alert(message?): void

Parameters

Name	Type
message?	string

Returns

void

Defined in

dist/types.d.ts:2399

---

atob

▸ atob(encodedData): string

atob decodes base64 into ascii text.

Parameters

Name	Type
encodedData	string

Returns

string

Defined in

globals.d.ts:761

▸ atob(encodedData): string

atob decodes base64 into ascii text.

Parameters

Name	Type
encodedData	string

Returns

string

Defined in

dist/types.d.ts:1172

---

btoa

▸ btoa(stringToEncode): string

btoa encodes ascii text into base64.

Parameters

Name	Type	Description
stringToEncode	string	The ascii text to encode.

Returns

string

Defined in

globals.d.ts:768

▸ btoa(stringToEncode): string

btoa encodes ascii text into base64.

Parameters

Name	Type	Description
stringToEncode	string	The ascii text to encode.

Returns

string

Defined in

dist/types.d.ts:1179

---

confirm

▸ confirm(message?): boolean

Parameters

Name	Type
message?	string

Returns

boolean

Defined in

globals.d.ts:1989

▸ confirm(message?): boolean

Parameters

Name	Type
message?	string

Returns

boolean

Defined in

dist/types.d.ts:2400

---

fetch

▸ fetch(url, init?): Promise<Response>

Send a HTTP(s) request

Parameters

Name	Type	Description
url	string	URL string
init?	RequestInit	A structured value that contains settings for the fetch() request.

Returns

Promise<Response>

A promise that resolves to Response object.

Defined in

globals.d.ts:987

▸ fetch(request, init?): Promise<Response>

Send a HTTP(s) request

Parameters

Name	Type	Description
request	Request	Request object
init?	RequestInit	A structured value that contains settings for the fetch() request.

Returns

Promise<Response>

A promise that resolves to Response object.

Defined in

globals.d.ts:1000

▸ fetch(url, init?): Promise<Response>

Send a HTTP(s) request

Parameters

Name	Type	Description
url	string	URL string
init?	RequestInit	A structured value that contains settings for the fetch() request.

Returns

Promise<Response>

A promise that resolves to Response object.

Defined in

dist/types.d.ts:1398

▸ fetch(request, init?): Promise<Response>

Send a HTTP(s) request

Parameters

Name	Type	Description
request	Request	Request object
init?	RequestInit	A structured value that contains settings for the fetch() request.

Returns

Promise<Response>

A promise that resolves to Response object.

Defined in

dist/types.d.ts:1411

---

prompt

▸ prompt(message?, _default?): string | null

Parameters

Name	Type
message?	string
_default?	string

Returns

string | null

Defined in

globals.d.ts:1990

▸ prompt(message?, _default?): string | null

Parameters

Name	Type
message?	string
_default?	string

Returns

string | null

Defined in

dist/types.d.ts:2401

---

removeEventListener

▸ removeEventListener<K>(type, listener, options?): void

Type parameters

Name	Type
K	extends "fetch"

Parameters

Name	Type
type	K
listener	(this: object, ev: EventMap[K]) => any
options?	boolean | EventListenerOptions

Returns

void

Defined in

globals.d.ts:1038

▸ removeEventListener(type, listener, options?): void

Parameters

Name	Type
type	string
listener	EventListenerOrEventListenerObject
options?	boolean | EventListenerOptions

Returns

void

Defined in

globals.d.ts:1043

▸ removeEventListener<K>(type, listener, options?): void

Type parameters

Name	Type
K	extends "fetch"

Parameters

Name	Type
type	K
listener	(this: object, ev: EventMap[K]) => any
options?	boolean | EventListenerOptions

Returns

void

Defined in

dist/types.d.ts:1449

▸ removeEventListener(type, listener, options?): void

Parameters

Name	Type
type	string
listener	EventListenerOrEventListenerObject
options?	boolean | EventListenerOptions

Returns

void

Defined in

dist/types.d.ts:1454

---

reportError

▸ reportError(error): void

Log an error using the default exception handler

Parameters

Name	Type	Description
error	any	Error or string

Returns

void

Defined in

globals.d.ts:1007

▸ reportError(error): void

Log an error using the default exception handler

Parameters

Name	Type	Description
error	any	Error or string

Returns

void

Defined in

dist/types.d.ts:1418