@sv2dev/multipart-stream

A utility to process multipart/form-data and multipart/mixed bodies.

Usage

import { streamParts, iterableToStream } from "@sv2dev/multipart-stream";

for await (const part of streamParts(responseOrRequest)) {
  if (part.type === "application/json") {
    console.log(await part.json());
  } else if (part.type === "text/plain") {
    console.log(await part.text());
  } else if (part.filename) {
    // Example for bun:
    const file = Bun.file(part.filename);
    const writer = file.writer();
    for await (const chunk of part) {
      await writer.write(chunk);
    }
    await writer.close();
  }
}

The streamParts() function returns an AsyncIterable<Part>. The Part class is similar to a Blob.

The streaming is designed to iterate over the parts and their bodies as they are received. If you don't process the body of a part while streaming, it will be skipped.

For example, if you use the Array.fromAsync() function to collect the parts, the body of each part will be neglected:

const [firstPart] = await Array.fromAsync(streamParts(responseOrRequest));

console.log(firstPart.type); // "application/json"
console.log(await firstPart.json()); // ERROR: The body is empty