FileBlob.write method | Bun module | Bun

FileBlob.write method | Bun module | BunBuild Docs Reference Guides Blog Discord/Bun/FileBlob/writeMwrite

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method

FileBlob.write write(data: string | ArrayBuffer | SharedArrayBuffer | BunFile | Request | Response | ArrayBufferViewArrayBufferLike>,options?: { highWaterMark: number }): Promisenumber>;

Write data to the file. This is equivalent to using Bun.write with a BunFile.

@param data

The data to write.

@param options

The options to use for the write.

Referenced typesclass ArrayBuffer

Represents a raw buffer of binary data, which is used to store data for the different typed arrays. ArrayBuffers cannot be read from or written to directly, but can be passed to a typed array or DataView Object to interpret the raw buffer as needed.

readonly [Symbol.toStringTag]: stringreadonly byteLength: number

Read-only. The length of the ArrayBuffer (in bytes).

resize(newByteLength?: number): void;

Resizes the ArrayBuffer to the specified size (in bytes).

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resize(byteLength: number): ArrayBuffer;

Resize an ArrayBuffer in-place.

slice(begin: number,end?: number): ArrayBuffer;

Returns a section of an ArrayBuffer.

transfer(newByteLength?: number): ArrayBuffer;

Creates a new ArrayBuffer with the same byte content as this buffer, then detaches this buffer.

MDN

transferToFixedLength(newByteLength?: number): ArrayBuffer;

Creates a new non-resizable ArrayBuffer with the same byte content as this buffer, then detaches this buffer.

MDN

interface SharedArrayBufferreadonly [Symbol.species]: SharedArrayBufferreadonly [Symbol.toStringTag]: 'SharedArrayBuffer'readonly byteLength: number

Read-only. The length of the ArrayBuffer (in bytes).

get growableget maxByteLengthgrow(newByteLength?: number): void;

Grows the SharedArrayBuffer to the specified size (in bytes).

MDN

grow(size: number): SharedArrayBuffer;

Grow the SharedArrayBuffer in-place.

slice(begin?: number,end?: number): SharedArrayBuffer;

Returns a section of an SharedArrayBuffer.

interface BunFile

Blob powered by the fastest system calls available for operating on files.

This Blob is lazy. That means it won't do any work until you read from it.

size will not be valid until the contents of the file are read at least once.type is auto-set based on the file extension when possible

const file = Bun.file("./hello.json");
console.log(file.type); // "application/json"
console.log(await file.text()); // '{"hello":"world"}'

lastModified: number

A UNIX timestamp indicating when the file was last modified.

readonly name?: string

The name or path of the file, as specified in the constructor.

readonly size: number

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readonly type: string

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arrayBuffer(): PromiseArrayBuffer>;

Returns a promise that resolves to the contents of the blob as an ArrayBuffer

bytes(): PromiseUint8ArrayArrayBufferLike>>;

MDN Reference

bytes(): PromiseUint8Array ArrayBuffer>>;

Returns a promise that resolves to the contents of the blob as a Uint8Array (array of bytes) its the same as new Uint8Array(await blob.arrayBuffer())

delete(): Promisevoid>;

Deletes the file (same as unlink)

exists(): Promiseboolean>;

Does the file exist?

This returns true for regular files and FIFOs. It returns false for directories. Note that a race condition can occur where the file is deleted or renamed after this is called but before you open it.

This does a system call to check if the file exists, which can be slow.

If using this in an HTTP server, it's faster to instead use return new Response(Bun.file(path)) and then an error handler to handle exceptions.

Instead of checking for a file's existence and then performing the operation, it is faster to just perform the operation and handle the error.

For empty Blob, this always returns true.

formData(): PromiseFormData>;

Read the data from the blob as a FormData object.

This first decodes the data from UTF-8, then parses it as a multipart/form-data body or a application/x-www-form-urlencoded body.

The type property of the blob is used to determine the format of the body.

This is a non-standard addition to the Blob API, to make it conform more closely to the BodyMixin API.

image(options?: ConstructorOptions): Image;

Wrap this blob in a Bun.Image pipeline. Equivalent to new Bun.Image(this, options) — the constructor is synchronous (the underlying read happens lazily when an Image terminal is awaited), so this works on Bun.file(), Bun.s3(), fd-backed and in-memory blobs alike:

await Bun.file("photo.jpg").image().resize(400).webp().write("thumb.webp");

json(): Promiseany>;

Read the data from the blob as a JSON object.

This first decodes the data from UTF-8, then parses it as JSON.

0, () will be slower on macOS" data-algolia-static="false" data-algolia-merged="false" data-type="Method">slice(begin?: number,end?: number,contentType?: string): BunFile;

Offset any operation on the file starting at begin and ending at end. end is relative to 0

Similar to TypedArray.subarray. Does not copy the file, open the file, or modify the file.

If begin > 0, () will be slower on macOS

@param begin

start offset in bytes

@param end

absolute offset in bytes (relative to 0)

@param contentType

MIME type for the new BunFile

slice(begin?: number,contentType?: string): BunFile;

Offset any operation on the file starting at begin

Similar to TypedArray.subarray. Does not copy the file, open the file, or modify the file.

If begin > 0, Bun.write() will be slower on macOS

@param begin

start offset in bytes

@param contentType

MIME type for the new BunFile

slice(contentType?: string): BunFile;

Slice the file from the beginning to the end, optionally with a new MIME type.

@param contentType

MIME type for the new BunFile

stat(): PromiseStats>;

Provides useful information about the file.

stream(): ReadableStream Uint8ArrayArrayBufferLike>>;

MDN Reference

stream(): ReadableStream Uint8Array ArrayBuffer>>;

Returns a readable stream of the blob's contents

text(): Promisestring>;

Returns a promise that resolves to the contents of the blob as a string

unlink(): Promisevoid>;

Deletes the file.

write(data: string | ArrayBuffer | SharedArrayBuffer | BunFile | Request | Response | ArrayBufferViewArrayBufferLike>,options?: { highWaterMark: number }): Promisenumber>;

Write data to the file. This is equivalent to using Bun.write with a BunFile.

@param data

The data to write.

@param options

The options to use for the write.

writer(options?: { highWaterMark: number }): FileSink;

Incremental writer for files and pipes.

class Request

This Fetch API interface represents a resource request.

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readonly body: null | ReadableStream Uint8ArrayArrayBufferLike>>

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readonly bodyUsed: boolean

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readonly cache: RequestCache

Returns the cache mode associated with request, which is a string indicating how the request will interact with the browser's cache when fetching.

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readonly credentials: RequestCredentials

Returns the credentials mode associated with request, which is a string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL.

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readonly destination: RequestDestination

Returns the kind of resource requested by request, e.g., "document" or "script".

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readonly headers: Headers

Returns a Headers object consisting of the headers associated with request. Note that headers added in the network layer by the user agent will not be accounted for in this object, e.g., the "Host" header.

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readonly integrity: string

Returns request's subresource integrity metadata, which is a cryptographic hash of the resource being fetched. Its value consists of multiple hashes separated by whitespace. [SRI]

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readonly keepalive: boolean

Returns a boolean indicating whether or not request can outlive the global in which it was created.

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readonly method: string

Returns request's HTTP method, which is "GET" by default.

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readonly mode: RequestMode

Returns the mode associated with request, which is a string indicating whether the request will use CORS, or will be restricted to same-origin URLs.

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readonly redirect: RequestRedirect

Returns the redirect mode associated with request, which is a string indicating how redirects for the request will be handled during fetching. A request will follow redirects by default.

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readonly referrer: string

Returns the referrer of request. Its value can be a same-origin URL if explicitly set in init, the empty string to indicate no referrer, and "about:client" when defaulting to the global's default. This is used during fetching to determine the value of the Referer header of the request being made.

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readonly referrerPolicy: ReferrerPolicy

Returns the referrer policy associated with request. This is used during fetching to compute the value of the request's referrer.

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readonly signal: AbortSignal

Returns the signal associated with request, which is an AbortSignal object indicating whether or not request has been aborted, and its abort event handler.

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readonly url: string

Returns the URL of request as a string.

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arrayBuffer(): PromiseArrayBuffer>;

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blob(): PromiseBlob>;

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bytes(): PromiseUint8ArrayArrayBufferLike>>;

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clone(): Request;

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