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XMLHttpRequest

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{{extdev}} {{extdev}}
- 
-==Using XMLHttpRequest== 
-===Introduction=== 
XMLHttpRequest is a Javascript object that was created by Microsoft and adopted by Mozilla. You can use it to easily retrieve data via HTTP. Despite its name, it can be used for more than just XML documents. XMLHttpRequest is a Javascript object that was created by Microsoft and adopted by Mozilla. You can use it to easily retrieve data via HTTP. Despite its name, it can be used for more than just XML documents.
-===Basic Usage===+==Basic Usage==
 +Using XMLHttpRequest is very simple. You create an instance of the object, open a URL, and send the request. The HTTP status code of the result, as well as the result document are available in the request object afterwards.
-Using XMLHttpRequest is very simple. You create an instance of the object, open a URL, and send the request. The HTTP status code of the result, as well as the result document are available in the request object afterwards.+===Example===
-====Example====+
<pre> <pre>
req = new XMLHttpRequest(); req = new XMLHttpRequest();
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Note that this example works synchronously, so it will block the user interface if you call this from your javascript. You should not use this in practice. Note that this example works synchronously, so it will block the user interface if you call this from your javascript. You should not use this in practice.
-===Asynchronous Usage===+==Asynchronous Usage==
 +If you intend to use XMLHttpRequest from an extension, you should let it load asynchronously. In asynchronous usage, you get a callback when the data has been received, which lets the browser continue to work as normal while your request is happening.
-If you intend to use XMLHttpRequest from an extension, you should let it load asynchronously. In asynchronous usage, you get a callback when the data has been received, which lets the browser continue to work as normal while your request is happening.+===Example===
-====Example====+
<pre> <pre>
req = new XMLHttpRequest(); req = new XMLHttpRequest();
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</pre> </pre>
-===Other Properties and Methods===+==Other Properties and Methods==
- +
In addition to the properties and methods shown above, there are other useful properties and methods on the request object. In addition to the properties and methods shown above, there are other useful properties and methods on the request object.
-====responseXML====+===responseXML===
- +
If you load an XML document, the responseXML property will contain the document as an XmlDocument object that you can manipulate using DOM methods. If you load an XML document, the responseXML property will contain the document as an XmlDocument object that you can manipulate using DOM methods.
-====setRequestHeader()====+===setRequestHeader()===
- +
This method can be used to set a HTTP header on the request before you send it. This method can be used to set a HTTP header on the request before you send it.
<pre> <pre>
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</pre> </pre>
-====getResponseHeader()====+===getResponseHeader()===
- +
This method can be used to get a HTTP header from the server response. This method can be used to get a HTTP header from the server response.
<pre> <pre>
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</ol> </ol>
-[[Category:Development|Using XMLHttpRequest]] [[Category:Example code|Using XMLHttpRequest]]+[[Category:Example code]] [[Category:Javascript example code]]

Revision as of 00:31, 6 March 2005

This page is part of the extension development documentation project.

Ask your questions in MozillaZine Forums. Also try browsing example code.

Note: development documentation is in process of being moved to Mozilla Development Center (MDC).

XMLHttpRequest is a Javascript object that was created by Microsoft and adopted by Mozilla. You can use it to easily retrieve data via HTTP. Despite its name, it can be used for more than just XML documents.

Contents

Basic Usage

Using XMLHttpRequest is very simple. You create an instance of the object, open a URL, and send the request. The HTTP status code of the result, as well as the result document are available in the request object afterwards.

Example

req = new XMLHttpRequest();
req.open('GET', 'http://www.mozilla.org/', false); 
req.send(null);
if(req.status == 200)
  dump(req.responseText);

Note that this example works synchronously, so it will block the user interface if you call this from your javascript. You should not use this in practice.

Asynchronous Usage

If you intend to use XMLHttpRequest from an extension, you should let it load asynchronously. In asynchronous usage, you get a callback when the data has been received, which lets the browser continue to work as normal while your request is happening.

Example

req = new XMLHttpRequest();
req.open('GET', 'http://www.mozilla.org/', true);
req.onreadystatechange = function (aEvt) {
  if (req.readyState == 4) {
     if(req.status == 200)
      dump(req.responseText);
     else
      dump("Error loading page\n");
  }
};
req.send(null); 

Other Properties and Methods

In addition to the properties and methods shown above, there are other useful properties and methods on the request object.

responseXML

If you load an XML document, the responseXML property will contain the document as an XmlDocument object that you can manipulate using DOM methods.

setRequestHeader()

This method can be used to set a HTTP header on the request before you send it.

req = new XMLHttpRequest();
req.open('GET', 'http://www.mozilla.org/', true);
req.setRequestHeader("X-Foo", "Bar");
req.send(null);

getResponseHeader()

This method can be used to get a HTTP header from the server response.

req = new XMLHttpRequest();
req.open('GET', 'http://www.mozilla.org/', true);
req.send(null);
dump("Content-Type: " + req.getResponseHeader("Content-Type") + "\n");

References

  1. XULPlanet documentation <li>Microsoft documentation <li>"Using the XMLHttpRequest Object" (jibbering.com) </ol>