An object of this type is returned by the files property of the HTML <input> element; this lets you access the list of files selected with the <input type="file"> element. It's also used for a list of files dropped into web content when using the drag and drop API; see the DataTransfer object for details on this usage.
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.
The readAsBinaryString method is used to start reading the contents of the specified Blob or File. When the read operation is finished, the readyState becomes DONE, and the loadend is triggered. At that time, the result attribute contains the raw binary data from the file.
The readAsDataURL method is used to read the contents of the specified Blob or File. When the read operation is finished, the readyState becomes DONE, and the loadend is triggered. At that time, the result attribute contains the data as a URL representing the file's data as a base64 encoded string.
The readAsText method is used to read the contents of the specified Blob or File. When the read operation is complete, the readyState is changed to DONE, the loadend is triggered, and the result attribute contains the contents of the file as a text string.
Returns 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.