open

Summary

Initializes an XMLHttpRequest.

Method of apis/xhr/XMLHttpRequest apis/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 / 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 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

Microsoft Developer Network: Windows Internet Explorer API reference Article