FileReader object

The FileReader object provides methods to asynchronously read a File or Blob, and events to obtain the results of these reads.

Syntax


var reader = new FileReader();

DOM Information

Inheritance Hierarchy

The FileReader does not inherit from any class or interface.

Members

The FileReader object has these types of members:

Events
Methods
Properties

Events

The FileReader object has these events.

Event	Description
onabort	ProgressEvent that occurs when a read or creation operation is aborted by calling the abort method.
onerror	ProgressEvent that fires when an error occurs during a read operation by an MSStreamReader or FileReader object.
onload	ProgressEvent that occurs when a read operation by an MSStreamReader or FileReader object successfully completes.
onloadend	ProgressEvent that occurs when a read operation by an MSStreamReader or FileReader object completes, even if the request fails.
onloadstart	ProgressEvent that occurs when a read operation is started by an MSStreamReader or FileReader object.
onprogress	ProgressEvent that occurs when an MSStreamReader or FileReader object reports progress about a read operation.

Methods

The FileReader object has these methods.

Method	Description
abort	Aborts a read operation by an MSStreamReader or FileReader object.
readAsArrayBuffer	Reads a File, Blob, MSStream into memory as an ArrayBuffer object.
readAsBinaryString	Reads the contents of a Blob or File as raw binary.
readAsDataURL	Reads a File or Blob object into memory as a data URL string.
readAsText	Reads a File, Blob, or MSStream object into memory as a text string.

Properties

The FileReader object has these properties.

Property	Access type	Description
error	Read-only	The error that occurred while reading a File, Blob, or MSStream object.
readyState		Contains a constant indicating the current state of the FileReader or MSStreamReader object.
result		The result of the read operation.

Remarks

The FileReader constructor returns a new FileReader object. The FileReader object enables asynchronous reads on individual File or Blob objects by firing progress events as the read occurs to event handler methods attached to the FileReader object.

A read operation will fail if a File or Blob is closed using the msClose method while the read operation is in progress.

Examples

JavaScript


var reader = new FileReader();
  
// Setup callback functions:
reader.onprogress = updateProgress;
reader.onload = loaded;
reader.onerror = errorHandler;
      
// Read file into memory as UTF-8:
reader.readAsText(readFile, "UTF-8");