@exact-realty/multipart-parser NPM

Multipart Message Parser

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This is a library for parsing MIME multipart messages, such as those used in HTTP requests and email messages, written in TypeScript. It provides an easy-to-use async generator that returns the parsed headers and body of each part in a multipart message. Nested multipart messages are supported.

Features

Parses multipart messages according to the specification
Supports nested multipart messages
Lightweight and fast
Written in TypeScript, but can be used with plain JavaScript as well
Well-tested

🚀 Installation

You can install the library using either npm or yarn:

npm install @exact-realty/multipart-parser

yarn add @exact-realty/multipart-parser

🎬 Usage

The library exports the function parseMultipartMessage, which returns an async generator that yields objects with the headers and body (as a Uint8Array) of each part in the multipart message.

📚 API

`parseMultipartMessage(stream: ReadableStream, boundary: string): AsyncGenerator`

This function takes a ReadableStream and a boundary string as arguments, and returns an asynchronous generator that yields objects with the following properties:

headers: a Headers object containing the headers of the current part
body: a Uint8Array containing the body of the current part, or null if the part is empty.
parts: a nested iterator of the same structure for any parts within the current part, if the part's Content-Type header indicates that it is a multipart message.

`boundaryRegex: RegExp`

A regular expression that can be used to validate a boundary string.

`boundaryMatchRegex: RegExp`

A regular expression that can be used to extract a boundary string from a Content-Type header.

`encodeMultipartMessage(boundary: string, msg: AsyncIterable<TDecodedMultipartMessage>): ReadableStream<ArrayBuffer>`

This function takes a boundary string and an array of messages as arguments and returns a ReadableStream that can be read to obtain a multipart message.

TDecodedMultipartMessage is defined as an object with the following fields:

headers: a Headers object containing the headers of the current part
body (optional): The body of the current part, or null if the part is empty. It can be any of the following types: ArrayBuffer, Blob, ReadableStream or any typed array, such as Uint8Array.
parts (optional): An async or sync iterable of one element or more of the same type (TDecodedMultipartMessage), for nested messages. If both body and parts are specified, body takes precedence.

Example

import { parseMultipartMessage } from '@exact-realty/multipart-message-parser';

const decoder = new TextDecoder();

const stream = ... // a ReadableStream containing the multipart message
const boundary = 'my-boundary'; // the boundary of the multipart message

for await (const part of parseMultipartMessage(stream, boundary)) {
  console.log(part.headers.get('content-type'));
  console.log(decoder.decode(part.body));
}