Multipart.ts

A TypeScript library for multipart data parsing and creation.

Documentation

Features

• Parse any kind of multipart/*, e.g. multipart/mixed, multipart/form-data, multipart/byteranges, etc.
• Create your own multipart with any parts
• Create a Multipart instance from FormData
• Serialise a Multipart instance into bytes (Uint8Array)
• Works with Node.js and in the browser without any polyfills
• Zero dependencies

Getting started

Install using NPM

npm i multipart-ts
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Import as native ESM

import {Multipart} from "multipart-ts";
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This library uses mainly Uint8Array so that it works in the browser. In Node.js, you can use Buffer as it is a superset of Uint8Array. In the browser, to convert a string to Uint8Array and vice-versa, use TextEncoder and TextDecoder respectively.

Example

node:http

import http from "node:http";
import {Component, Multipart} from "multipart-ts";

http.createServer(async (req, res) => {
    // Parse multipart request body
    if (req.method === "POST" && req.headers["content-type"]) {

        // get the request body
        const body: Uint8Array[] = [];
        for await (const chunk of req)
            body.push(chunk);

        // create a blob to hold the Content-Type header (which includes the boundary) and the body
        const blob = new Blob(body, {type: req.headers["content-type"]});
        // parse multipart from the blob
        const multipart = await Multipart.blob(blob);
        console.log(multipart);

        res.end("ok");
    }
    // Return a multipart response
    else if (req.method === "GET") {
        const multipart = new Multipart(
            [
                new Component({
                    "X-Foo": "Bar Baz",
                    "Content-Type": "text/plain"
                }, Buffer.from("Hello world!")),

                // You can add nested multipart components
                new Multipart([
                    new Component({"Content-Type": "application/json"}, Buffer.from(JSON.stringify({foo: "bar"}))),
                    new Component({}, [0x66, 0x6f, 0x6f, 0x20, 0x62, 0x61, 0x72])
                ])
            ],
            "your-custom-boundary", // or omit to generate a random one
            "multipart/mixed"
        );
        // use the content-type header generated by the multipart
        res.setHeader("Content-Type", multipart.headers.get("Content-Type")!);
        // send the multipart body bytes
        res.end(multipart.body);
    }
    else res.end();
}).listen(3000);
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Browser

import {Multipart, Component} from "multipart-ts";

//create
const multipart = new Multipart(
    [new Component({"Content-Type": "text/plain"}, new TextEncoder().encode("Hello world!"))],
    "your-custom-boundary", // or omit to generate a random one
    "multipart/mixed"
);

// parse
const data: Uint8Array = multipart.bytes();
const parsed: Multipart = Multipart.parse(data);

console.log(new TextDecoder().decode(parsed.parts[0].body)); // Hello world!
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Licence

Copyright © 2024–2025 Zefir Kirilov.

This project is licensed under the GNU Lesser General Public License v3.0 (LGPL-3.0). A copy of the licence text is included in this repository. If not, see https://www.gnu.org/licenses/.