javascript

Chapter 21: Upcoming API s
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“ copyLink ” — dropEffect “ copy ” and “ link ” are allowed.
“ copyMove ” — dropEffect “ copy ” and “ move ” are allowed.
“ linkMove ” — dropEffect “ link ” and “ move ” are allowed.
“ all ” — All dropEffect values are allowed.
This property must be set inside the ondragstart event handler.
Suppose that you want to allow a user to move text from a text box into a < div > . To accomplish this, you
must set both dropEffect and effectAllowed to “ move ” . The text won ’ t automatically move itself
because the default behavior for the drop event on a < div > is to do nothing. If you override the default
behavior, the text is automatically removed from the text box. It is then up to you to insert it into the
< div > to finish the action. If you were to change dropEffect and effectAllowed to “ copy ” , the text
in the text box would not automatically be removed.
Additional Members
The HTML 5 specification indicates the following additional methods on the dataTransfer object:
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addElement( element ) — Adds an element to the drag operation. This is purely for data
purposes and doesn ’ t affect the appearance of the drag operation.
clearData( format ) — Clears the data being stored with the particular format. This has been
implemented in IE, Firefox, Chrome, and Safari.
setDragImage( element , x , y ) — Allows you to specify an image to be displayed under the
cursor as the drag takes place. This method accepts three arguments: an HTML element to
display, and the x - and y - coordinates on the image where the cursor should be positioned. The
HTML element may be an image, in which case the image is displayed, or any other element, in
which case a rendering of the element is displayed. Safari is the only browser that has this
method; however, it doesn ’ t appear to work.
types — A list of data types currently being stored. This is not yet implemented in any browsers.
The WebSocket Type
Another interesting addition to HTML 5 is the WebSocket type, a facility for enabling bidirectional
communication between the browser and server. The WebSocket constructor takes a single argument
that indicates the URL with which to make the connection. This URL must specify the ws or wss protocol
and an absolute URL. A connection to the URL is initiated as soon as the constructor is called. Here’s an
example:
var socket = new WebSocket(“ws://www.yourdomain.com/connect/”);
The current state of the WebSocket object can be determined by using the readyState property, whose
value will be one of the following: 0 to indicate that it ’ s connecting, 1 to indicate that the connection is
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