Assigns method, destination URL, and other optional attributes of a pending request.

Syntax

object.open(sMethod, sUrl [, bAsync] [, sUser] [, sPassword])

Parameters

sMethod	Required. String that specifies the HTTP method used to open the connection: such as GET, POST, or HEAD. This parameter is not case-sensitive.
sUrl	Required. String that specifies either the absolute or a relative URL of the XML data or server-side XML Web services.
bAsync	Optional. Variant that specifies true for asynchronous operation (the call returns immediately), or false for synchronous operation. If true, assign a callback handler to the onreadystatechange property to determine when the call has completed. If not specified, the default is true. Performance Note   When bAsync is set to false, send operations are synchronous, and Windows Internet Explorer does not accept input or produce output while send operations are in progress. Therefore, this setting should not be used in situations where it is possible for a user to be waiting on the send operation to complete.
sUser	Optional. Variant that specifies the name of the user for authentication. If this parameter is null ("") or missing and the site requires authentication, the component displays a logon window.
sPassword	Optional. Variant that specifies the password for authentication. This parameter is ignored if the user parameter is null ("") or missing.

Return Value

No return value.

Remarks

open was introduced in Internet Explorer 7.

The following HTTP verbs and World Wide Web Distributed Authoring and Versioning (WebDAV) methods are supported:

Verb / Method	Defined In HTTP (RFC-2616)	Defined In WebDAV (RFC-2518)	Function
GET	HTTP	WebDAV	Request URI
POST	HTTP	WebDAV	Send data to server
HEAD	HTTP	WebDAV	Request URI without body
PUT	HTTP	WebDAV	Store data for URI
DELETE	HTTP	WebDAV	Delete data for URI
MOVE		WebDAV	Move URI to to new location
PROPFIND		WebDAV	Request URI Properties
PROPPATCH		WebDAV	Update or Delete URI Properties
MKCOL		WebDAV	Create collection at URI
COPY		WebDAV	Create copy of URI
LOCK		WebDAV	Create Lock
UNLOCK		WebDAV	Remove Lock
OPTIONS	HTTP	WebDAV	Request URI Options

Internet Explorer caches the results of HTTP GET requests in the Temporary Internet Files (TIF) folder. In most cases, caching improves performance for data that will not change frequently. To guarantee that the results are not cached, use POST.

Security Alert   Cross-domain, cross-port, and mixed protocol requests are not allowed. The sUrl parameter may only specify files in the same domain, using the same port and protocol method, as that from which the page is served.

Although this method accepts credentials passed via parameter, those credentials are not automatically sent to the server on the first request. The sUser and sPassword parameters are not transmitted unless the server challenges the client for credentials with a 401 - Access Denied response.

After calling this method, use send to send the request and data, if any, to the server.

Standards Information

This method is defined in The XMLHttpRequest Object (W3C Working Draft) .

Applies To

XMLHttpRequest, XMLHttpRequest Constructor

See Also

abort, onreadystatechange, Communicating XML Data over the Web with WebDAV