XMLHttpRequest

Utilize os objetos XMLHttpRequest (XHR) para interagir com os servidores. Pode obter os dados de um URL sem ter que recarregar toda a página. Isto permite que uma página da Web atualize apenas parte da mesma, sem interromper o que o utilizador está a fazer. XMLHttpRequest é totalmente utilizado na programação Ajax.

História

XMLHttpRequest was originally designed by Microsoft around 1999 and later adopted by Mozilla, Apple, and Google. Since October 2014, it has been standardized at the WHATWG, together with the new promise-based fetch() (en-US) method.

Despite its name, XMLHttpRequest can be used to retrieve any type of data, not just XML, and it supports protocols other than HTTP (including file and ftp).

XMLHttpRequest() (en-US)

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

This interface also inherits properties of XMLHttpRequestEventTarget (en-US) and of EventTarget (en-US).

XMLHttpRequest.onreadystatechange (en-US)

An EventHandler (en-US) that is called whenever the readyState attribute changes.

XMLHttpRequest.readyState (en-US) Read only

Returns an unsigned short, the state of the request.

XMLHttpRequest.response (en-US) Read only

Returns an ArrayBuffer (en-US), Blob, Document, JavaScript object, or a DOMString, depending on the value of XMLHttpRequest.responseType (en-US). that contains the response entity body.

XMLHttpRequest.responseText (en-US) Read only

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

XMLHttpRequest.responseType (en-US)

Is an enumerated value that defines the response type.

XMLHttpRequest.responseURL (en-US) Read only

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

XMLHttpRequest.responseXML (en-US) 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 workers.

XMLHttpRequest.status (en-US) Read only

Returns an unsigned short with the status of the response of the request.

XMLHttpRequest.statusText (en-US) Read only

Returns a DOMString containing the response string returned by the HTTP server. Unlike XMLHTTPRequest.status (en-US), this includes the entire text of the response message ("200 OK", for example).

XMLHttpRequest.timeout (en-US)

Is an unsigned long representing the number of milliseconds a request can take before automatically being terminated.

XMLHttpRequestEventTarget.ontimeout

Is an EventHandler (en-US) that is called whenever the request times out.

XMLHttpRequest.upload (en-US) Read only

Is an XMLHttpRequestUpload, representing the upload process.

XMLHttpRequest.withCredentials (en-US)

Is a Boolean (en-US) that indicates whether or not cross-site Access-Control requests should be made using credentials such as cookies or authorization headers.

XMLHttpRequest.channel (en-US)Read only

Is a nsIChannel. The channel used by the object when performing the request.

XMLHttpRequest.mozAnon (en-US)Read only

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

XMLHttpRequest.mozSystem (en-US)Read only

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

XMLHttpRequest.mozBackgroundRequest (en-US)

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

XMLHttpRequest.mozResponseArrayBuffer (en-US) Obsolete since Gecko 6 Read only

Is an ArrayBuffer. The response to the request, as a JavaScript typed array.

XMLHttpRequest.multipart (en-US)Obsolete since Gecko 22

This Gecko-only feature, a boolean, was removed in Firefox/Gecko 22. Please use Server-Sent Events, Web Sockets, or responseText from progress events instead.

onreadystatechange as a property of the XMLHttpRequest instance is supported in all browsers.

Since then, a number of additional event handlers were implemented in various browsers (onload, onerror, onprogress, etc.). These are supported in Firefox. In particular, see nsIXMLHttpRequestEventTarget and Using XMLHttpRequest.

More recent browsers, including Firefox, also support listening to the XMLHttpRequest events via standard addEventListener APIs in addition to setting on* properties to a handler function.

XMLHttpRequest.abort() (en-US)

Aborts the request if it has already been sent.

XMLHttpRequest.getAllResponseHeaders() (en-US)

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

XMLHttpRequest.getResponseHeader() (en-US)

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() (en-US)

Initializes a request. This method is to be used from JavaScript code; to initialize a request from native code, use openRequest() instead.

XMLHttpRequest.overrideMimeType() (en-US)

Overrides the MIME type returned by the server.

XMLHttpRequest.send() (en-US)

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

XMLHttpRequest.setRequestHeader() (en-US)

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

XMLHttpRequest.init()

Initializes the object for use from C++ code.

XMLHttpRequest.openRequest()

Initializes a request. This method is to be used from native code; to initialize a request from JavaScript code, use open() instead. See the documentation for open().

XMLHttpRequest.sendAsBinary()

A variant of the send() method that sends binary data.

• Tutoriais da MDN abrangendo XMLHttpRequest:
  • Ajax — Getting Started
  • Using XMLHttpRequest
  • HTML in XMLHttpRequest
  • FormData
• HTML5 Rocks — New Tricks in XMLHttpRequest2
• Chrome scope availability — how to access XMLHttpRequest from JSM modules etc., which do not have access to DOM
  • Components.utils.importGlobalProperties
  • nsIXMLHttpRequest