HTML and CSS Reference
In-Depth Information
validated against the schema. If there are any validation errors, the
ValidationEventHandler
event is
raised. The event-handler function
OnValidationError
stores the XML file name and the error message in a
generic list.
Once all the uploaded XML files are validated, the code iterates through the generic list of errors and
creates a bulleted list of the error messages. The error list is returned to the jQuery
success
function by
converting it to JSON format.
To test the application, run it and try uploading XML files—some matching the schema and some
violating the schema (for example, keep some
<employee>
elements without an
employeeid
attribute). You
should get error messages for any invalid XML files.
Summary
HTML5's File API allows you to read files residing in the user's local file system. The files, however, must be
explicitly selected by the user using a file field control's Open File dialog or by dragging them from
Windows Explorer and dropping them onto a predefined area of a web page.
The File API consists of three main objects:
File
,
FileList
, and
FileReader
. The
File
object gives
information about a file such as its name, size, and MIME type. The
FileList
object is a collection of
File
objects and is obtained either via the
iles
property of a file field or via the
iles
property of a
dataTransfer
object. The
FileReader
object lets you read selected files in asynchronous fashion.
Although drag-and-drop is an independent feature of HTML5, it can be coupled with the File API to
enhance the user experience. Selected files can be uploaded to the server using the
$.ajax()
method.
The next chapter introduces another interesting feature—web workers—that allows you to run code
in the background. Web workers are like threads used in a multithreaded desktop application in that they
let you run lengthy processes in the background without obstructing the user interface.
