- React

Multiple file upload is able to:

- Accept one or more files via browse or drag-and-drop
- Provide their data to you using file objects via the `onFileDrop` callback prop
- Read files as dataURLs, calling provided callbacks as needed when files start/finish being read, as well as when the read succeeds or fails
- Display (in real time) the upload progress/status of each file
  - Uploaded files are represented by the multiple file upload status item component, this component includes the aforementioned built-in file reading logic
  - If you prefer to supply your own file reading logic and strictly use multiple file upload status item as a display component, the `customFileHandler`, `fileName`, `fileSize`, `progressValue`, and `progressVariant` props exist to allow you to do that

## Restricting file size and type

As with singular file upload, any props accepted by react-dropzone’s Dropzone component can be passed as a dropzoneProps object in order to customize the behavior of the Dropzone, such as restricting the type of files allowed. The following examples will only accept the files they list as accepted. Note that file type determination is not reliable across platforms (see the note on react-dropzone’s docs about the accept prop), so be sure to test the behavior of your file upload restriction on all browsers and operating systems targeted by your application.

### IMPORTANT: A note about security

Restricting file sizes and types in this way is for user convenience only, and it cannot prevent a malicious user from submitting anything to your server. As with any user input, your application should also validate, sanitize and/or reject restricted files on the server side.

## Composable structure

File upload - multiple is designed in a composable manner to make customization easier. The standard sub-component relationships are arranged as follows:

    <MultipleFileUpload>
      <MultipleFileUploadMain />
      <MultipleFileUploadStatus>
        <MultipleFileUploadStatusItem />
      </MultipleFileUploadStatus>
    </MultipleFileUpload>

## Examples

### Basic

The below example demonstrates a typical application of file upload - multiple, with a few tweaks from that typical application to enhance the convenience of the example.

The “Show as horizontal” checkbox can be used to easily toggle the `isHorizontal` prop, showing our available styling variations.

The “Demonstrate error reporting by forcing uploads to fail” checkbox shows how our `progressHelperText` prop can be used to provide status messages to users, such as when a file fails to upload. While this checkbox is checked it will cause any file uploaded to automatically fail the file reading process, and helper text will be dynamically rendered which informs the user of that error.

## Types

Multiple file upload uses the `DropzoneOptions` type from react-dropzone. It is comprised of additional props with their own types. For more information on using `DropzoneOptions` visit react-dropzone props and methods.

Additionally, it calls the `onFileDrop` callback with an event of type `DropEvent`. `DropEvent` is a union comprised of the following types:

     React.DragEvent<HTMLElement>
     | React.ChangeEvent<HTMLInputElement>
     | DragEvent
     | Event

##
CSS variables