XMLHttpRequest

Fundamental to almost all applications that call themselves Ajax based is the creation of a component known as the XMLHttpRequest object.

So you create a variable in JavaScript with var, give it a name (like "request" ), and then assign it to a new instance of XMLHttpRequest.

From the point of view of the XMLHttpRequest object, the interaction occurs within the existing security configuration.

and hide all this logic in a XmlHttpRequest service, of course, and support multiple concurrent requests.

As a result, your Ajax code (and specifically, the XMLHttpRequest object) can only make requests to the same domain on which it's running.

It's your job then, to go beyond a simple application and that requires a more thorough understanding of XMLHttpRequest.

If your Web page was served from a. com, then you can only make Ajax (or more precisely, XMLHttpRequest) calls to a. com.

It's very important to understand that there is no guarantee that XMLHttpRequests will complete in the order they were dispatched.

A simpler solution is to pass all requests from XMLHttpRequest through a proxy resource located on the same domain as the loaded page.

This property, available on XMLHttpRequest, returns the server's response in the form of a DOM document.

At the time of this writing, the XMLHttpRequest is supported in different ways in different browsers.

The XMLHttpRequest object is what's usually used, but it's definitely not the only way.

Thus, it would be nice to simply change XMLHttpRequest's name to something more accurate, like HttpRequest, or perhaps simply Request.

However, some older versions of browsers allow making XMLHttpRequest connections to the domain specified at the document. domain property.

You use the XmlHttpRequest or equivalent object that modern browsers provide for this asynchronous background communication.

For each venue, the script then makes a call back to the Foursquare proxy to get the details of the venue using XMLHttpRequest, as usual.

An alternative is to upload the page yourself using XmlHTTPRequest and connect to a REST service.

You parse the document in the onreadystatechange function of the XMLHttpRequest object used to make the Ajax call.

You wouldn't use XMLHttpRequest this time because you want the page to be refreshed after the POST request.

To accomplish this, you can register a callback function with the XMLHttpRequest and then dispatch the XMLHttpRequest asynchronously.

Dojo also provides APIs for making asynchronous XMLHttpRequest calls for fetching data from the server without refreshing the page.

That code is "200" and is reported through the status property of the XMLHttpRequest object.

Because of this, references to the document, window, DOMParser, and XMLHttpRequest objects cannot be resolved.

Because its browser-based interface has access to the XMLHttpRequest object, the DOH can support asynchronous unit tests.

To invoke the Web service, notice that you use the standard JavaScript API XMLHttpRequest.

Next, I set a header on the XMLHttpRequest stating that the content of the request is form-encoded data.

Whenever you send sensitive data over an XmlHTTPRequest, use proper authentication and secure tunneling.

datajs uses XMLHttpRequest to make network calls by default, but a different HTTP client can be used.

Unfortunately, XMLHttpRequest isn't an approved standard, and vendor support varies slightly.

That's exactly what's happened with XMLHttpRequest, the basic object used in Ajax apps.

With Ajax, the JavaScript code uses the XMLHttpRequest object to communicate directly with the server.

As I show in Listing 3, all the XMLHTTPRequest object provides is a callback mechanism called onreadystatechange.

Use false as a condition that means the XMLHttpRequest object isn't created yet.

The readyState property of XMLHttpRequest is a numeric value that gives the status of the request's lifecycle.

You should remember from the last article that the XMLHttpRequest object has a property called readyState.

The script then uses the XMLHttpRequest object to perform an HTTP operation against a server.

Later, I'll discuss techniques to handle browsers that don't support XMLHttpRequest.

The final script, server. js, uses the special XMLHttpRequest object that is now a standard feature of modern browsers.

From this diagram you can see exactly how the XMLHttpRequest object functions.

The first step in this Ajax roundtrip is to create an XMLHttpRequest instance.

For now, the examples assume that the newXMLHttpRequest function from Listing 2 will always return an XMLHttpRequest instance.

Hold open an XMLHttpRequest connection until a response is received.

In these cases, you can use the responseXML property of the XMLHttpRequest object to retrieve the data.

You'll use false as a condition that means the XMLHttpRequest object hasn't been created yet.

Listing 3 shows the AJAX method, which involves the use of the XMLHttpRequest call to refresh the portal page inside the portlet.

The wrapper function sends an XMLHttpRequest to the server.

We created a simple helper function to support using the XMLHttpRequest object to invoke services using E4X.

When you made the call to the server using the XMLHttpRequest object, you registered a response handler.

The snippet in Listing 6 creates an instance of the XMLHttpRequest object in the ajaxPost method.

The widget uses Dojo's xhrGet function to issue an XMLHTTPRequest to the server.

In addition, this function deletes the previous XMLHttpRequest objects from the memory to prevent a memory leak in the Web browser.

To send this, you need to use the XMLHTTPRequest object.

Browsers now have tabs, CSS, and XmlHttpRequest, but their HTML renderers are stuck in 1999.

If this is undesirable, you can still pre-load the assets using XMLHttpRequest.

Listing 4 shows how to initialize the XMLHttpRequest for cross-browser support.

Microsoft, for example, invented the XHR object which makes AJAX possible.

XMLHttpRequest - what it is, how to perform a complete GET request, how to detect errors.

A formalization of the de-facto standard XMLHttpRequest object, the centerpiece of Ajax communication

A Web Service Client that wraps XMLHttpRequest