Consuming a Web service using Javascript

Question

Is there a way to consume a web service using JavaScript? I'm Looking for a built-in way to do it, using a JavaScript framework is not an option.

Answer 1

You can consume a web service using JavaScript natively using the XmlHttpRequest object. However instantiating this object varies between browsers. For example Firefox and IE 7+ let you instantiate it as a native JavaScript object but IE6 requires you to instantiate it as an ActiveX control.

Because of this I'd recommend using an abstraction library such as jQuery. If that's not an option then abstract the creation into a factory method and check for the browser version.

To use this to make a web service call you simply instantiate the object and then call it's open() method. I recommend this is done async to keep the UI responsive. When invoked async you will get callbacks to your specified async method that will indicate the status of the request. When the status is 4 (loaded) you can take the response data and then process it.

How you process the data will depend on what it is, if it's JSON then you can run it through JavaScript's eval() method but that does have some security implications. If it's XML you can use the XML DOM to process it.

See Wikipedia for more info on the XMLHttpRequest object.