XMLHttpRequest

XMLHttpRequest (XHR) objects are used to interact with servers. You can retrieve data from a URL without having to do a full page refresh. This enables a Web page to update just part of a page without disrupting what the user is doing.

XMLHttpRequest is used heavily in AJAX programming.

EventTarget XMLHttpRequestEventTarget XMLHttpRequest

Despite its name, XMLHttpRequest can be used to retrieve any type of data, not just XML.

If your communication needs to involve receiving event data or message data from a server, consider using server-sent events through the EventSource interface. For full-duplex communication, WebSockets may be a better choice.

Note: This feature is available in Web Workers, except for Service Workers

Constructor

XMLHttpRequest()

The constructor initializes an XMLHttpRequest. It must be called before any other method calls.

Properties

This interface also inherits properties of XMLHttpRequestEventTarget and of EventTarget.

XMLHttpRequest.readyState Read only

Returns a number representing the state of the request.

XMLHttpRequest.response Read only

Returns an ArrayBuffer, a Blob, a Document, a JavaScript object, or a string, depending on the value of XMLHttpRequest.responseType, that contains the response entity body.

XMLHttpRequest.responseText Read only

Returns a string that contains the response to the request as text, or null if the request was unsuccessful or has not yet been sent.

XMLHttpRequest.responseType

Specifies the type of the response.

XMLHttpRequest.responseURL Read only

Returns the serialized URL of the response or the empty string if the URL is null.

XMLHttpRequest.responseXML Read only

Returns a Document containing the response to the request, or null if the request was unsuccessful, has not yet been sent, or cannot be parsed as XML or HTML. Not available in Web Workers.

XMLHttpRequest.status Read only

Returns the HTTP response status code of the request.

XMLHttpRequest.statusText Read only

Returns a string containing the response string returned by the HTTP server. Unlike XMLHttpRequest.status, this includes the entire text of the response message ("OK", for example).

Note: According to the HTTP/2 specification RFC 7540, section 8.1.2.4: Response Pseudo-Header Fields, HTTP/2 does not define a way to carry the version or reason phrase that is included in an HTTP/1.1 status line.

XMLHttpRequest.timeout

The time in milliseconds a request can take before automatically being terminated.

XMLHttpRequest.upload Read only

A XMLHttpRequestUpload representing the upload process.

XMLHttpRequest.withCredentials

Returns true if cross-site Access-Control requests should be made using credentials such as cookies or authorization headers; otherwise false.

Non-standard properties

XMLHttpRequest.channel Read only

The channel used by the object when performing the request.

XMLHttpRequest.mozAnon Read only

A boolean. If true, the request will be sent without cookie and authentication headers.

XMLHttpRequest.mozSystem Read only

A boolean. If true, the same origin policy will not be enforced on the request.

XMLHttpRequest.mozBackgroundRequest

A boolean. It indicates whether or not the object represents a background service request.

Methods

XMLHttpRequest.abort()

Aborts the request if it has already been sent.

XMLHttpRequest.getAllResponseHeaders()

Returns all the response headers, separated by CRLF, as a string, or null if no response has been received.

XMLHttpRequest.getResponseHeader()

Returns the string containing the text of the specified header, or null if either the response has not yet been received or the header doesn't exist in the response.

XMLHttpRequest.open()

Initializes a request.

XMLHttpRequest.overrideMimeType()

Overrides the MIME type returned by the server.

XMLHttpRequest.send()

Sends the request. If the request is asynchronous (which is the default), this method returns as soon as the request is sent.

XMLHttpRequest.setRequestHeader()

Sets the value of an HTTP request header. You must call setRequestHeader() after open(), but before send().

Events

abort

Fired when a request has been aborted, for example because the program called XMLHttpRequest.abort(). Also available via the onabort event handler property.

error

Fired when the request encountered an error. Also available via the onerror event handler property.

load

Fired when an XMLHttpRequest transaction completes successfully. Also available via the onload event handler property.

loadend

Fired when a request has completed, whether successfully (after load) or unsuccessfully (after abort or error). Also available via the onloadend event handler property.

loadstart

Fired when a request has started to load data. Also available via the onloadstart event handler property.

progress

Fired periodically when a request receives more data. Also available via the onprogress event handler property.

readystatechange

Fired whenever the readyState property changes. Also available via the onreadystatechange event handler property.

timeout

Fired when progress is terminated due to preset time expiring. Also available via the ontimeout event handler property.

Specifications

Specification
XMLHttpRequest Standard
# interface-xmlhttprequest

Browser compatibility

BCD tables only load in the browser

See also