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open

Summary

Initializes an XMLHttpRequest.

Method of apis/xhr/XMLHttpRequestapis/xhr/XMLHttpRequest

Syntax

 object.open(method, url, async, user, password);

Parameters

method

Data-type
String

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

url

Data-type
String

Specifies either an absolute or relative URL of the XML data or server-side Web services.

async

Data-type
Boolean

(Optional)

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.

user

Data-type
String

(Optional)

Specifies the name of the user for authentication. If this parameter is null or not specified and the site requires authentication, the browser displays a logon window.

password

Data-type
String

(Optional)

Specifies the password for authentication. This parameter is ignored if the user parameter is null or not specified.

Return Value

No return value

Examples

The following script demonstrates how to create and use the XMLHttpRequest object. For best client-side performance, the request is asynchronous and uses an onreadystatechange event handler to process the data returned by the call.

function handler() {
  if (xhr.readyState === 4 /* complete */) {
    if (xhr.status === 200) {
            console.log(xhr.responseText);
        }
    }
}
var xhr = new XMLHttpRequest();
xhr.open("GET", "http://localhost/test.xml", true);
xhr.onreadystatechange = handler;
xhr.send();

Notes

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
GETHTTPWebDAVRequest URI
POSTHTTPWebDAVSend data to server
HEADHTTPWebDAVRequest URI without body
PUTHTTPWebDAVStore data for URI
DELETEHTTPWebDAVDelete 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
UNLOCKWebDAVRemove Lock
OPTIONSHTTPWebDAVRequest 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 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.

Related specifications

W3C XMLHttpRequest Specification
W3C Working Draft

Attributions