Ajax and the Yahoo! Connection Manager, Page 3
It is becoming more and more common to submit form values through an Ajax request instead of using the traditional form posting technique. The Yahoo! Connection Manager makes this easy by allowing you to set a form whose data should be sent through the request. For instance, suppose you have a form with the ID of "frmInfo". You could set up a POST request to submit the data contained in the form like so:
var oForm = document.getElementById("frmInfo"); YAHOO.util.Connect.setForm(oForm); YAHOO.util.Connect.asyncRequest("post", "datahandler.php", oCallback);
setForm() method, the Connection Manager creates a string of data to be send in the next request. Because of this, there is no need to specify the fourth argument for the
asyncRequest() method, since all the data is already retrieved from the form.
It's important to note that the data string is constructed when you call
setForm(), not when
asyncRequest() is called. The data being sent is the data at the time when setForm() was called, so this method should only be called right before a call to
asyncRequest(), to ensure that the data is the most recent available.
setProgId() like so:
Here, the Connection Manager will attempt to create an ActiveX object with the signature "some.future.ActiveX.signature" before it attempts to create an object from the known list of signatures. This is something that Yahoo! provided to future-proof the library (though Internet Explorer 7 will feature a native
XMLHttpRequest object as other browsers now do; this may not be necessary). Unlike other methods, this method sets the signature string for all requests.
You can also send header information by using the
initHeader() method, such as:
YAHOO.util.Connect.initHeader("MyName", "Nicholas"); YAHOO.util.Connect.asyncRequest("get", "info.php", oCallback);
In this example, an extra header with a name of "MyName" and a value of "Nicholas" is sent to the server. Note that this header is only good for one request; all headers reset to default values after each request.
There's no need to set the "Content-type" header for POST requests. The Connection Manager handles this for you behind the scenes.
While the Yahoo! Connection Manager does make some requests easier, it does have its limitations. Currently, only asynchronous requests are supported, so you'll be stuck using old school XMLHttp is you need to make a synchronous request. Though many argue that synchronous requests should never be used, sometimes there are practical reasons for it.
It is also worth noting that this is version 0.9 of the Connection Manager, so undoubtedly there will be some additions and changes in the future. However, for the time being, it remains one of the most compact libraries for cross-browser XMLHttp available.
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