Introduction
During MIX11, I attended a very interesting session about datajs which was presented by Asad Khan and Marcelo Lopez Ruiz. As I promised in my previous post, in this post, I’ll show you how to make a JSONP call to a WCF Data Service using the datajs library.
A little about datajs
datajs is a very promising JavaScript library which is currently being built by Microsoft as an Open Source in CodePlex. The library as described in its CodePlex site as “a new cross-browser JavaScript library that enables data-centric web applications by leveraging modern protocols such as JSON and OData and HTML5-enabled browser features. It's designed to be small, fast, and easy to use”. Some of its current features are the ability to communicate with OData services and APIs to work with local data through browser features such as Web Storage (and in the future, IndexedDB). For further reading about datajs, go to its documentation, or download the library and play with it (there is also a NuGet package for it).
Making a JSONP call using datajs
Here is the implementation of the same JSONP call functionality from the previous post but using datajs:
<!DOCTYPE html>
<html>
<head id="Head1" runat="server">
<title>JSONP Call using datajs</title>
<script src="Scripts/datajs-0.0.3.min.js" type="text/javascript"></script>
</head>
<body>
<form id="form1" runat="server">
<output id="result">
</output>
</form>
<script type="text/javascript">
OData.defaultHttpClient.enableJsonpCallback = true;
OData.read("http://localhost:23330/SchoolDataService.svc/Courses",
function (data, request) {
var output = document.getElementById('result');
for (var i = 0; i < data.results.length; i++) {
var div = document.createElement('div');
div.innerHTML = data.results[i].Title;
output.appendChild(div);
}
});
</script>
</body>
</html>
A few things to notice in the example:
- I add the script to datajs which exists in my web application project under the Scripts directory.
- You need to enable JSONP through
OData.defaultHttpClient.enableJsonpCallback, which is disabled by default. - Use the
OData.Read function to make the call to the service (no need to add the format or callback query parameters like I did in the previous post since they are added automatically).
Pay attention that in a real world application, you would probably like to disable JsonpCallback after you make the call.
Summary
datajs is still in Alpha version, and it is only in its starting point. It tries to provide a common solution around the data problem in client-side development. I expect it to grow and to supply more capabilities in the future. In this post, I showed how to use it in order to make a JSONP call to a JSONP enabled WCF Data Service.
