extract-files

What is extract-files?

The extract-files package is designed to extract files from a JavaScript object tree so they can be uploaded via a multipart request. It is commonly used in applications that need to handle file uploads, especially in the context of GraphQL operations.

What are extract-files's main functionalities?

Extract files from an object

This feature allows you to extract files from an object, which is useful when preparing files for upload. The `extractFiles` function takes an object and a path to traverse within the object to find files. It returns an object with the extracted files and a clone of the original object with files replaced by null.

{"operation": "const { extractFiles } = require('extract-files');\nconst file = new File(['content'], 'file.txt', { type: 'text/plain' });\nconst operation = { variables: { file } };\nconst { files, clone } = extractFiles(operation, 'variables');"}

Support for FileList and Map objects

The package can handle `FileList` objects, which are typically obtained from file input elements, and `Map` objects. It can extract files from these complex structures, making it versatile for various file upload scenarios.

{"operation": "const { extractFiles } = require('extract-files');\nconst fileList = document.querySelector('input[type=file]').files;\nconst operation = { variables: { files: fileList } };\nconst { files, clone } = extractFiles(operation, 'variables');"}

Other packages similar to extract-files

form-data

The form-data package allows you to create `multipart/form-data` streams to submit files and values via HTTP. It can be used to simulate a form submission with file uploads, similar to extract-files, but it is more focused on constructing the form data itself rather than extracting files from an existing object structure.

busboy

Busboy is a Node.js module for parsing incoming HTML form data, including file uploads. It differs from extract-files in that it is used on the server side to process file uploads, whereas extract-files is typically used on the client side to prepare files for upload.

multer

Multer is a Node.js middleware for handling `multipart/form-data`, primarily used for uploading files. It is similar to busboy but is designed to be used with Express applications. Unlike extract-files, multer is not about extracting files from an object but rather about handling file uploads on the server side.

README

extract-files

Clones a value, recursively extracting File, Blob and ReactNativeFile instances with their object paths, replacing them with null. FileList instances are treated as File instance arrays.

Used by GraphQL multipart request spec client implementations such as graphql-react and apollo-upload-client.

Usage

Install with npm:

npm install extract-files

See the extractFiles documentation to get started.

Support

• Node.js v6+
• Browsers > 0.5%, not dead
• React Native

API

Table of contents

• class ReactNativeFile
  • Examples
• function extractFiles
  • Examples
• type ExtractableFile
• type ExtractFilesResult
• type ObjectPath
  • See
  • Examples
• type ReactNativeFileSubstitute
  • See
  • Examples

class ReactNativeFile

Used to mark a React Native File substitute in an object tree for extractFiles. It’s too risky to assume all objects with uri, type and name properties are files to extract.

Parameter	Type	Description
file	ReactNativeFileSubstitute	A React Native File substitute.

Examples

An extractable file in React Native.

import { ReactNativeFile } from 'extract-files'

const file = new ReactNativeFile({
  uri: uriFromCameraRoll,
  name: 'a.jpg',
  type: 'image/jpeg'
})

function extractFiles

Clones a value, recursively extracting File, Blob and ReactNativeFile instances with their object paths, replacing them with null. FileList instances are treated as File instance arrays.

Parameter	Type	Description
value	*	Value (typically an object tree) to extract files from.
path	ObjectPath? = ''	Prefix for object paths for extracted files.

Returns: ExtractFilesResult — Result.

Examples

Extract files from an object.

For the following:

import { extractFiles } from 'extract-files'

const file1 = new File(['1'], '1.txt', { type: 'text/plain' })
const file2 = new File(['2'], '2.txt', { type: 'text/plain' })
const value = {
  a: file1,
  b: [file1, file2]
}

const { clone, files } = extractFiles(value, 'prefix')

value remains the same.

clone is:

{
  a: null,
  b: [null, null]
}

files is a Map instance containing:

Key	Value
file1	['prefix.a', 'prefix.b.0']
file2	['prefix.b.1']

type ExtractableFile

An extractable file.

Type: File | Blob | ReactNativeFile

type ExtractFilesResult

What extractFiles returns.

Type: Object

Property	Type	Description
clone	*	Clone of the original input value with files recursively replaced with null.
files	Map<ExtractableFile, Array<ObjectPath>>	Extracted files and their locations within the original value.

type ObjectPath

String notation for the path to a node in an object tree.

Type: String

See

• object-path on npm.

Examples

Object path is property a, array index 0, object property b.

a.0.b

type ReactNativeFileSubstitute

A React Native File substitute for when using FormData.

Type: Object

Property	Type	Description
uri	String	Filesystem path.
name	String?	File name.
type	String?	File content type.

See

• React Native FormData polyfill source.

Examples

A camera roll file.

{
  uri: uriFromCameraRoll,
  name: 'a.jpg',
  type: 'image/jpeg'
}

Changelog

5.0.0

Major

• extractFiles has a new return signature and no longer mutates the original input, fixing #8. It returns an object with clone, a clone of the original input value with files recursively replaced with null, and files, a Map instance keying each extracted file to an array of object paths.

Minor

• Files can now be used as the root value passed to extractFiles.

Patch

• Updated dev dependencies.
• Updated package description.
• Moved JSDoc type definitions into the index file.
• Manually composed package exports instead of relying on *.
• Improved tests.
• Added a paragraph explaining the GraphQL use case to the readme.