Categories: AJAX

XMLHttpRequest Object in Ajax

XMLHttpRequest (XHR) is an API available to web browser scripting languages such as JavaScript. It is used to send HTTP or HTTPS requests to a web server and load the server response data back into the script. Development versions of all major browsers support URI schemes beyond http: and https:, in particular, blob: URLs are supported.An object of XMLHttpRequest is used for asynchronous communication between client and server.

It performs following operations:

  • Sends data from the client in the background
  • Receives the data from the server
  • Updates the webpage without reloading it.

Properties of XMLHttpRequest object

The common properties of XMLHttpRequest object are as follows:

onReadyStateChange-
It is called whenever readystate attribute changes. It must not be used with synchronous requests.

readyState-
represents the state of the request. It ranges from 0 to 4.
0 UNOPENED open() is not called.
1 OPENED open is called but send() is not called.
2 HEADERS_RECEIVED send() is called, and headers and status are available.
3 LOADING Downloading data; responseText holds the data.
4 DONE The operation is completed fully.

reponseText-
returns response as text.

responseXML-
returns response as XML

Methods of XMLHttpRequest object-

The important methods of XMLHttpRequest object are as follows:

void open(method, URL):
opens the request specifying get or post method and url.

void open(method, URL, async):
same as above but specifies asynchronous or not.

void open(method, URL, async, username, password):
same as above but specifies username and password.

void send():
sends get request.

void send(string):
send post request.

setRequestHeader(header,value):
it adds request headers.

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).

Create an XMLHttpRequest Object-

To create an instance of XMLHttpRequest, simply do this:

var myRequest = new XMLHttpRequest();

Old versions of Internet Explorer (IE5 and IE6) use an ActiveX Object:

var xmlhttp=new ActiveXObject(“Microsoft.XMLHTTP”);

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Dinesh Rajput

Dinesh Rajput is the chief editor of a website Dineshonjava, a technical blog dedicated to the Spring and Java technologies. It has a series of articles related to Java technologies. Dinesh has been a Spring enthusiast since 2008 and is a Pivotal Certified Spring Professional, an author of a book Spring 5 Design Pattern, and a blogger. He has more than 10 years of experience with different aspects of Spring and Java design and development. His core expertise lies in the latest version of Spring Framework, Spring Boot, Spring Security, creating REST APIs, Microservice Architecture, Reactive Pattern, Spring AOP, Design Patterns, Struts, Hibernate, Web Services, Spring Batch, Cassandra, MongoDB, and Web Application Design and Architecture. He is currently working as a technology manager at a leading product and web development company. He worked as a developer and tech lead at the Bennett, Coleman & Co. Ltd and was the first developer in his previous company, Paytm. Dinesh is passionate about the latest Java technologies and loves to write technical blogs related to it. He is a very active member of the Java and Spring community on different forums. When it comes to the Spring Framework and Java, Dinesh tops the list!

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