HTML and CSS Reference
In-Depth Information
Property
Description
timeout
Specifies the number of milliseconds to wait before terminating a request. A value of
0
indicates no timeout.
upload
Tracks the progress of the data upload.
In a typical usage, you set
responseType
and
timeout
before initiating a request. You then track the
readyState
of the request and, when it becomes
4
(complete), access the
responseText
,
responseXML
,
status
, and
statusText
properties.
Methods of XMLHttpRequest
The
XMLHttpRequest
object provides methods that allow you to initiate a request, send data with the
request, and terminate a request before its completion. Table 11-2 lists these methods for your quick
reference.
Table 11-2.
Methods of the
X
MLHttpRequest
Object
Method
Description
open()
Sets the HTTP method and request URL before the request is made. By
default, a request is made in asynchronous fashion, but you can make a
request synchronously using a parameter.
send()
Actually sends a request to the server. For all request types other than
GET
, you
can also pass data as a parameter. The type of data depends on the content
type of the request.
abort()
Cancels a request before its completion.
getResponseHeader()
Returns the value of a specified HTTP response header once a request is
complete.
getAllResponseHeaders()
Returns all the HTTP response headers once a request is complete.
setRequestHeader()
Sets a request header (such as
Content-Type
). This method must be called
between
open()
and
send()
.
In a typical usage, you call the
open()
method followed by
setRequestHeader()
, and then call
send()
to
actually make the request. In most cases, you use the
GET
or
POST
verb with the
open()
method. However,
open()
can be used for other verbs too. For example, while using the ASP.NET Web API, you need to pass
PUT
and
DELETE
in addition to
GET
and
POST
.
send()
can be used to send data depending on the content type. Common data formats are text and
JSON. You can also use
FormData
object to bundle data as key-value pairs and send it to the server.
Events of XMLHttpRequest
Events of the
XMLHttpRequest
object allow you to track the request being made and determine its status.
Table 11-3 lists these events.
