the processing and queuing engine for react-uploady

Usage no npm install needed!

<script type="module">
  import rpldyUploader from 'https://cdn.skypack.dev/@rpldy/uploader';


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The Uploader is the processing and queuing engine for React-Uploady. When files are handed to the Uploader, it will represent each file as a Batch Item and group them together in Batches. This is for the most part internal to the uploading mechanism.

The Uploader fires Batch & BatchItem lifecycle events that can be registered to. Some of these events also allow to cancel uploads dynamically.

_If you're looking to integrate file upload with your React app, you'd probably want to head over to the @rpldy/uploady README.


  $ yarn add @rpldy/uploader

  $ npm i @rpldy/uploader


When in React, you don't need to use this package directly. Uploady will take care of initialization and other aspects (ie: event registration) for you. In case you want to create your own uploader instance, you can do it like so:

import createUploader, { UPLOADER_EVENTS } from "@rpldy/uploader";

const uploader = createUploader({ 
    autoUpload: false,
    grouped: true,

uploader.on(UPLOADER_EVENTS.ITEM_START, (item) => {
     console.log(`item ${item.id} started uploading`);  


Upload Options

Name (* = mandatory) Type Default Description
autoUpload boolean true automatically upload files when they are added
destination Destination undefined configure the end-point to upload to
inputFieldName string "file" name (attribute) of the file input field (requires sendWithFormData = true)
grouped boolean false group multiple files in a single request
maxGroupSize number 5 maximum of files to group together in a single request
formatGroupParamName (number, string) => string undefined determine the upload request field name when more than file is grouped in a single upload
fileFilter (File | string, index: number, File[] | string[]) => boolean | Promise<boolean> undefined return false or Promise resolving to false to exclude item from batch
method string "POST" HTTP method in upload request
params Object undefined collection of params to pass along with the upload (requires sendWithFormData = true)
forceJsonResponse boolean false parse server response as JSON even if no JSON content-type header received
withCredentials boolean false set XHR withCredentials to true
enhancer UploaderEnhancer undefined uploader enhancer function
concurrent boolean false issue multiple upload requests simultaneously
maxConcurrent number 2 maximum allowed simultaneous requests
send SendMethod @rpldy/sender how to send files to the server
sendWithFormData boolean true upload is sent as part of formdata - when true, additional params can be sent along with uploaded data
formatServerResponse FormatServerResponseMethod undefined function to create the batch item's uploadResponse from the raw xhr response
formDataAllowUndefined boolean false //whether to include params with undefined value

Uploader API


(files: UploadInfo | UploadInfo[], options?: ?UploadOptions) => void

The way to add file(s) to be uploaded. Second parameters allows to pass different options than the ones the instance currently uses for this specific batch. These options will be merged with current instance options.


() => void

For batches that were added with autoUpload = false, the upload method must be called for the files to begin uploading.


(id?: string) => void

abort all files being uploaded or a single item by its ID


(id: string) => void

abort a specific batch by its ID


(options: UploadOptions) => UploaderType

options parameter will be merged with the instance's existing options Returns the uploader instance


() => CreateOptions

get the instance's upload options


() => void

remove all batches that were added with autoUpload = false and were not sent to upload yet.



register an event handler



register an event handler that will be called only once



unregister an existing event handler


(name: any, Object) => void

Extensions can only be registered by enhancers. If registerExtension is called outside an enhancer, an error will be thrown Name must be unique. If not, an error will be thrown


(name: any) => ?Object_

Retrieve a registered extension by its name


The Uploader will trigger for batch and batch-item lifecycle events.

Registering to handle events can be done using the uploader's on() and once() methods. Unregistering can be done using off() or by the return value of both on() and once().

const batchAddHandler = (batch) => {};

const unregister = uploader.on(UPLOADER_EVENTS.BATCH_ADD, batchAddHandler);

unregister(); //is equivalent to the line below
uploader.off(UPLOADER_EVENTS.BATCH_ADD, batchAddHandler);


Triggered when a new batch is added.

  • Parameters: (batch, uploadOptions)

This event is cancellable


Triggered when batch items start uploading

  • Parameters: (batch)

This event is cancellable


Triggered every time progress data is received from the upload request(s)

  • Parameters: (batch)


Triggered when batch items finished uploading

  • Parameters: (batch)


Triggered in case batch was cancelled from BATCH_START event handler

  • Parameters: (batch)


Triggered in case the batch was aborted

  • Parameters: (batch)


Triggered in case the batch was failed with an error. These errors will most likely occur due to invalid event handling. For instance, by a handler (ex: BATCH_START) throwing an error.

  • Parameters: (batch)


Triggered when all batch items have finished uploading or in case the batch was cancelled(abort) or had an error

  • Parameters: (batch)


Triggered when item starts uploading (just before) For grouped uploads (multiple files in same xhr request) ITEM_START is triggered for each item separately

  • Parameters: (item)

This event is cancellable


Triggered when item finished uploading successfully

  • Parameters: (item)

The server response can be accessed through the item's uploadResponse property and status code through uploadStatus


Triggered every time progress data is received for this file upload

  • Parameters: (item)

progress info is accessed through the item's "completed" (percentage) and "loaded" (bytes) properties.


Triggered in case item was cancelled from ITEM_START event handler

  • Parameters: (item)


Triggered in case item upload failed

  • Parameters: (item)

The server response can be accessed through the item's uploadResponse property.


Triggered in case abort was called

  • Parameters: (item)


Triggered for item when uploading is done due to: finished, error, cancel or abort Use this event if you want to handle the state of the item being done for any reason.

  • Parameters: (item)


Triggered before a group of items is going to be uploaded Group will contain a single item unless "grouped" option is set to true.

Handler receives the item(s) in the group and the upload options that were used. The handler can change data inside the items and in the options by returning different data than received. See this guide for more details.

  • Parameters: (items, options)

This event is cancellable


Triggered when abort is called without an item id (abort all)

  • no parameters

Cancellable Events

These are events that allow the client to cancel their respective upload object (batch or batch-item) To cancel the upload, the handler must return (boolean) false.

uploader.on(UPLOADER_EVENTS.ITEM_START, (item) => {
    let result;
    if (item.file.name.endsWith(".xml")) {
        result = false; //only false will cause a cancel.

    return result;