The FileReader object lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.

File objects may be obtained from a FileList object returned as a result of a user selecting files using the <input> element, from a drag and drop operation's DataTransfer object, or from the mozGetAsFile() API on an HTMLCanvasElement.

Constructor

FileReader()

Returns a newly constructed FileReader.

See Using files from web applications for details and examples.

Properties

FileReader.error Read only

A DOMError representing the error that occurred while reading the file.

FileReader.readyState Read only

A number indicating the state of the FileReader. This is one of the following:

EMPTY	0	No data has been loaded yet.
LOADING	1	Data is currently being loaded.
DONE	2	The entire read request has been completed.

FileReader.result Read only

The file's contents. This property is only valid after the read operation is complete, and the format of the data depends on which of the methods was used to initiate the read operation.

Event handlers

FileReader.onabort

A handler for the abort event. This event is triggered each time the reading operation is aborted.

FileReader.onerror

A handler for the error event. This event is triggered each time the reading operation encounter an error.

FileReader.onload

A handler for the load event. This event is triggered each time the reading operation is successfully completed.

FileReader.onloadstart

A handler for the loadstart event. This event is triggered each time the reading is starting.

FileReader.onloadend

A handler for the loadend event. This event is triggered each time the reading operation is completed (either in success or failure).

FileReader.onprogress

A handler for the progress event. This event is triggered while reading a Blob content.