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open method

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


var retval = XMLHttpRequest.open(bstrMethod, bstrUrl, varAsync, varUser, varPassword);


bstrMethod [in]

Type: String

String that specifies the HTTP method used to open the connection: such as GET, POST, or HEAD. This parameter is not case-sensitive.

bstrUrl [in]

Type: String

String that specifies either the absolute or a relative URL of the XML data or server-side Web services.

varAsync [in, optional]

Type: Variant

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 varAsync is set to false, send operations are synchronous. When a send operation is in progress, other operations are suspended. This affects user input, display updates, and similar tasks. As a result, this setting should not be used when users expect to interact with an app while a send operation is active.

varUser [in, optional]

Type: Variant

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.

varPassword [in, optional]

Type: Variant

Variant that specifies the password for authentication. This parameter is ignored if the user parameter is null ("") or missing.

Standards information


open was introduced in Windows Internet Explorer 7.

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

Verb / MethodDefined In HTTP (RFC-2616)Defined In WebDAV (RFC-2518)Function
POSTHTTPWebDAVSend data to server
HEADHTTPWebDAVRequest URI without body
PUTHTTPWebDAVStore data for URI
MOVEWebDAVMove URI to to new location
PROPFINDWebDAVRequest URI Properties
PROPPATCHWebDAVUpdate or Delete URI Properties
MKCOLWebDAVCreate collection at URI
COPYWebDAVCreate copy of URI
LOCKWebDAVCreate Lock


Windows 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 Warning:   Cross-domain, cross-port, and mixed protocol requests are not allowed. The bstrUrl 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 varUser and varPassword 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.

See also

Other Resources
Communicating XML Data over the Web with WebDAV



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