file-type
- Version 20.0.0
- Published
- 102 kB
- 4 dependencies
- MIT license
Install
npm i file-type
yarn add file-type
pnpm add file-type
Overview
Detect the file type of a file, stream, or data
Index
Variables
Functions
Classes
Type Aliases
Variables
variable supportedExtensions
const supportedExtensions: ReadonlySet<string>;
Supported file extensions.
variable supportedMimeTypes
const supportedMimeTypes: ReadonlySet<string>;
Supported MIME types.
Functions
function fileTypeFromBlob
fileTypeFromBlob: (blob: Blob) => Promise<FileTypeResult | undefined>;
Detect the file type of a [
Blob
](https://nodejs.org/api/buffer.html#class-blob) or [File
](https://developer.mozilla.org/en-US/docs/Web/API/File).Parameter blob
The [
Blob
](https://nodejs.org/api/buffer.html#class-blob) used for file detection.Returns
The detected file type, or
undefined
when there is no match.Example 1
import {fileTypeFromBlob} from 'file-type';const blob = new Blob(['<?xml version="1.0" encoding="ISO-8859-1" ?>'], {type: 'text/plain',endings: 'native'});console.log(await fileTypeFromBlob(blob));//=> {ext: 'txt', mime: 'text/plain'}
function fileTypeFromBuffer
fileTypeFromBuffer: ( buffer: Uint8Array | ArrayBuffer) => Promise<FileTypeResult | undefined>;
Detect the file type of a
Uint8Array
, orArrayBuffer
.The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the buffer.
If file access is available, it is recommended to use
.fromFile()
instead.Parameter buffer
An Uint8Array or ArrayBuffer representing file data. It works best if the buffer contains the entire file. It may work with a smaller portion as well.
Returns
The detected file type, or
undefined
when there is no match.
function fileTypeFromFile
fileTypeFromFile: ( filePath: string, options?: { customDetectors?: Iterable<Detector> }) => Promise<FileTypeResult | undefined>;
Detect the file type of a file path.
The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the file.
This is for Node.js only.
To read from a [
File
](https://developer.mozilla.org/docs/Web/API/File), seefileTypeFromBlob()
.The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the buffer.
Returns
The detected file type and MIME type or
undefined
when there is no match.
function fileTypeFromStream
fileTypeFromStream: ( stream: AnyWebReadableStream<Uint8Array> | NodeReadableStream) => Promise<FileTypeResult | undefined>;
Detect the file type of a [web
ReadableStream
](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream).If the engine is Node.js, this may also be a [Node.js
stream.Readable
](https://nodejs.org/api/stream.html#stream_class_stream_readable).Direct support for Node.js streams will be dropped in the future, when Node.js streams can be converted to Web streams (see [
toWeb()
](https://nodejs.org/api/stream.html#streamreadabletowebstreamreadable-options)).The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the buffer.
Parameter stream
A [web
ReadableStream
](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) or [Node.jsstream.Readable
](https://nodejs.org/api/stream.html#stream_class_stream_readable) streaming a file to examine.Returns
A
Promise
for an object with the detected file type, orundefined
when there is no match.
function fileTypeFromTokenizer
fileTypeFromTokenizer: ( tokenizer: ITokenizer) => Promise<FileTypeResult | undefined>;
Detect the file type from an [
ITokenizer
](https://github.com/Borewit/strtok3#tokenizer) source.This method is used internally, but can also be used for a special "tokenizer" reader.
A tokenizer propagates the internal read functions, allowing alternative transport mechanisms, to access files, to be implemented and used.
Parameter tokenizer
File source implementing the tokenizer interface.
Returns
The detected file type, or
undefined
when there is no match.An example is [
@tokenizer/http
](https://github.com/Borewit/tokenizer-http), which requests data using [HTTP-range-requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests). A difference with a conventional stream and the [*tokenizer*](https://github.com/Borewit/strtok3#tokenizer), is that it is able to *ignore* (seek, fast-forward) in the stream. For example, you may only need and read the first 6 bytes, and the last 128 bytes, which may be an advantage in case reading the entire file would take longer.Example 1
import {makeTokenizer} from '@tokenizer/http';import {fileTypeFromTokenizer} from 'file-type';const audioTrackUrl = 'https://test-audio.netlify.com/Various%20Artists%20-%202009%20-%20netBloc%20Vol%2024_%20tiuqottigeloot%20%5BMP3-V2%5D/01%20-%20Diablo%20Swing%20Orchestra%20-%20Heroines.mp3';const httpTokenizer = await makeTokenizer(audioTrackUrl);const fileType = await fileTypeFromTokenizer(httpTokenizer);console.log(fileType);//=> {ext: 'mp3', mime: 'audio/mpeg'}
function fileTypeStream
fileTypeStream: { ( readableStream: NodeReadableStream, options?: StreamOptions ): Promise<ReadableStreamWithFileType>; (webStream: AnyWebByteStream, options?: StreamOptions): Promise<any>;};
Returns a
Promise
which resolves to the original readable stream argument, but with an addedfileType
property, which is an object like the one returned fromfileTypeFromFile()
.This method can be handy to put in between a stream, but it comes with a price. Internally
stream()
builds up a buffer ofsampleSize
bytes, used as a sample, to determine the file type. The sample size impacts the file detection resolution. A smaller sample size will result in lower probability of the best file type detection.Parameter readableStream
A [web
ReadableStream
](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) or [Node.jsstream.Readable
](https://nodejs.org/api/stream.html#stream_class_stream_readable), streaming a file to examine.Parameter options
May be used to override the default sample size.
Returns
A
Promise
which resolves to the original readable stream argument, but with an addedfileType
property, which is an object like the one returned fromfileTypeFromFile()
.Example 1
import got from 'got';import {fileTypeStream} from 'file-type';const url = 'https://upload.wikimedia.org/wikipedia/en/a/a9/Example.jpg';const stream1 = got.stream(url);const stream2 = await fileTypeStream(stream1, {sampleSize: 1024});if (stream2.fileType?.mime === 'image/jpeg') {// stream2 can be used to stream the JPEG image (from the very beginning of the stream)}
Classes
class FileTypeParser
class FileTypeParser extends DefaultFileTypeParser {}
Extending
FileTypeParser
with Node.js engine specific functions.
method fromFile
fromFile: (filePath: string) => Promise<FileTypeResult | undefined>;
method fromStream
fromStream: ( stream: AnyWebReadableStream<Uint8Array> | NodeReadableStream) => Promise<FileTypeResult | undefined>;
Parameter stream
Node.js
stream.Readable
or webReadableStream
.
method toDetectionStream
toDetectionStream: { ( readableStream: NodeReadableStream, options?: StreamOptions ): Promise<ReadableStreamWithFileType>; (webStream: any, options?: StreamOptions): Promise<any>;};
Works the same way as fileTypeStream, additionally taking into account custom detectors (if any were provided to the constructor).
class TokenizerPositionError
class TokenizerPositionError extends Error {}
constructor
constructor(message?: string);
Type Aliases
type AnyWebReadableByteStreamWithFileType
type AnyWebReadableByteStreamWithFileType = AnyWebReadableStream<Uint8Array> & { readonly fileType?: FileTypeResult;};
type AnyWebReadableStream
type AnyWebReadableStream<G> = WebReadableStream<G> | ReadableStream<G>;
Either the Node.js ReadableStream or the
lib.dom.d.ts
ReadableStream. Related issue: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/60377
type Detector
type Detector = { id: string; detect: ( tokenizer: ITokenizer, fileType?: FileTypeResult ) => Promise<FileTypeResult | undefined>;};
A custom file type detector.
Detectors can be added via the constructor options or by directly modifying
FileTypeParser#detectors
.Detectors provided through the constructor options are executed before the default detectors.
Custom detectors allow for: - Introducing new
FileTypeResult
entries. - Modifying the detection behavior of existingFileTypeResult
types.### Detector execution flow
If a detector returns
undefined
, the following rules apply:1. **No Tokenizer Interaction**: If the detector does not modify the tokenizer's position, the next detector in the sequence is executed. 2. **Tokenizer Interaction**: If the detector modifies the tokenizer's position (
tokenizer.position
is advanced), no further detectors are executed. In this case, the file type remainsundefined
, as subsequent detectors cannot evaluate the content. This is an exceptional scenario, as it prevents any other detectors from determining the file type.### Example usage
Below is an example of a custom detector array. This can be passed to the
FileTypeParser
via thefileTypeOptions
argument.import {FileTypeParser} from 'file-type';const customDetectors = [async tokenizer => {const unicornHeader = [85, 78, 73, 67, 79, 82, 78]; // "UNICORN" in ASCII decimalconst buffer = new Uint8Array(unicornHeader.length);await tokenizer.peekBuffer(buffer, {length: unicornHeader.length, mayBeLess: true});if (unicornHeader.every((value, index) => value === buffer[index])) {return {ext: 'unicorn', mime: 'application/unicorn'};}return undefined;},];const buffer = new Uint8Array([85, 78, 73, 67, 79, 82, 78]);const parser = new FileTypeParser({customDetectors});const fileType = await parser.fromBuffer(buffer);console.log(fileType); // {ext: 'unicorn', mime: 'application/unicorn'}Parameter tokenizer
The [tokenizer](https://github.com/Borewit/strtok3#tokenizer) used to read file content.
Parameter fileType
The file type detected by standard or previous custom detectors, or
undefined
if no match is found.Returns
The detected file type, or
undefined
if no match is found.
type FileTypeOptions
type FileTypeOptions = { customDetectors?: Iterable<Detector>;};
type FileTypeResult
type FileTypeResult = { /** One of the supported [file types](https://github.com/sindresorhus/file-type#supported-file-types). */ readonly ext: string;
/** The detected [MIME type](https://en.wikipedia.org/wiki/Internet_media_type). */ readonly mime: string;};
type ReadableStreamWithFileType
type ReadableStreamWithFileType = NodeReadableStream & { readonly fileType?: FileTypeResult;};
type StreamOptions
type StreamOptions = { /** The default sample size in bytes.
@default 4100 */ readonly sampleSize?: number;};
Package Files (2)
Dependencies (4)
Dev Dependencies (8)
Peer Dependencies (0)
No peer dependencies.
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