TL;DR

A polyfill for Request.prototype.formData on cloudflare workers because they're not compliant to the whatwg spec even though their documentation suggests otherwise.

Installation

npm install @ssttevee/cfw-formdata-polyfill

Usage

import `@ssttevee/cfw-formdata-polyfill`;

// get req from handler

const fd = await req.formData();

or if a ponyfill is more preferrable

import FormDataFromRequest from '@ssttevee/cfw-formdata-polyfill/ponyfill';

// get req from handler

const fd = await FormDataFromRequest.call(req);

Examples

There are some full examples in the examples directory.

Native Request.prototype.formData on Cloudflare Workers

Since before the public launch of Cloudflare Workers until the time of writing, Request.prototype.formData has been able to handle application/x-www-form-urlencoded payloads as one would expect. However, their support for multipart/form-data has been... undocumented.

Native multipart/form-data support

The native Request.prototype.formData does technically support multipart/form-data. However, files are returned as binary strings rather than a Blob. That means the filename and content type metadata is lost. Though this is somewhat justified upon closer inspection of the environment.

The FormData API

The FormData API, as long as no files are involved, seems to work as one would expect. However, advanced users will quickly realize that it cannot be used to construct multipart/form-data payloads to be used with fetch. It doesn't even accept any type other than strings. This is because the Blob API doesn't exist on Cloudflare Workers.

The Blob API

The Blob API, as designed for the browser, is meant to be an abstraction for reading arbitrary data, outside of the browser sandbox, from the operating system. Meanwhile, there is no parallel in the Cloudflare Workers environment. This, I believe, is the primary reason that this halfway point for the FormData API exists on Cloudflare Workers.

Polyfilling

This package was designed to be used in conjuction with a bundler -- I prefer rollup -- to fix Request.prototype.formData and to be able to use it for receiving multipart/form-data uploads.