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A multipart/form-data middleware based on busboy library.



$ npm i @marblejs/middleware-multipart

Requires @marblejs/core to be installed.


import { multipart$ } from '@marblejs/middleware-multipart';

Type declaration

multipart$ :: ParserOpts -> HttpMiddlewareEffect


parameter definition
options <optional> ParserOpts


parameter definition
files <optional> Array<string>
stream <optional> StreamHandler
maxFileSize <optional> number
maxFileCount <optional> number
maxFieldSize <optional> number
maxFieldCount <optional> number


{% hint style="warning" %} Make sure that you always handle the files that a user uploads. Never add it as a global middleware since a malicious user could upload files to a route that you didn't handle. Only use this it on routes where you are handling the uploaded files. {% endhint %}

In-memory storage:

import { multipart$ } from '@marblejs/middleware-multipart';

const effect$ = r.pipe(
  r.useEffect(req$ => req$.pipe(
    map(req => ({ body: {
      files: req.files,    // file data
      body: req.body,      // all incoming body fields

Out-of-memory storage:

import { multipart$, StreamHandler } from '@marblejs/middleware-multipart';

const stream: StreamHandler = ({ file, fieldname }) => {
  // stream here incoming file to different location...
  const destination = // ... and grab the persisted file location
  return of({ destination });

const effect$ = r.pipe(
  r.useEffect(req$ => req$.pipe(
      maxFileCount: 1,
      files: ['image_1'],
    map(req => ({ body: {
      files: req.files['image_1'],  // file data
      body: req.body,               // all incoming body fields

You can intercept incoming files and stream them to the different place, eg. to OS filesystem or AWS S3 bucket. The prervious example shows how you can specify constraints for multipart/form-data parsing the accepts only one image_1 field.

Each file included inside req.files object contains the following information:

key description
fieldname Field name specified in the form
filename Name of the file on the user's computer
encoding Encoding type of the file
mimetype Mime type of the file
size Size of the file in bytes (in-memory parsing)
destination The place in which the file has been saved (if not in-memory parsing)
buffer A Buffer of the entire file (in-memory parsing)

You can define the following middleware options:

key description
maxFileCount The total count of files that can be sent
maxFieldCount The total count of fields that can be sent
maxFileSize The max possible file size in bytes
files An array of acceptable field names
stream A handler which you can use to stream incoming files to different location
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