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JQuery AJAX Http polling example |
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This article examines a way of creating a polling AJAX http request. This is a request that will run every N seconds based on a value. It will hit a remote service and return a result, and display that result on screen.
View a full demo of an AJAX polling request here.
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Cross site AJAX HttpRequest problems and how to create a Proxy handler |
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Most of us are familiar with the AJAX post() and getJSON() methods of remotely calling and passing around data, I use them with abundance when building applications. One thing I had not considered until recently is that all my AJAX Http requests are usually internal to that application, which also means they are on the same server and domain.
I recently jumped into a project where the application spanned 24 domains, and had been developed to use a core component library to help code re use. The problem with this arose when you are on one domain (www.domain1.com) and you want to make a request to a different domain (www.domain2.com). You encounter something called the 'same-Origin' policy.
This article deals with how to create a proxy to handle cross site AJAX http Requests.
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JQuery Datatables plugin example using a server side data request (coldfusion) |
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Im my previous article on how to use the JQuery datatables plug I concentrated mainly on the JQuery script, and how to build the AJAX request to receive a JSON response.
In this article I will demonstrate the full application which will include the front end JQuery, building the back end server response and a few tips that I've picked up since implementing the plugin. I am using an MS SQL table filled with UK location data that I also used for a weather webservice, to fill the table.
A full example of this working can be seen here: Data table server side example
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What does "Invalid Label" mean in a JSON response, and how can I fix it? |
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I recently build an application that returned a JSON object of data based on a select field value. Whilst I was building this I encountered an error using the JavaScript eval() function on my JSON response. I am using the eval() function to parse a string from my JSON response, but firebug is showing a JavaScript error of "Invalid Label".
This is the code:
2 jsonResponse = eval(data);
3 var src = jsonResponse.DATA;
4 });
After having a Google around it appears that the eval function is interpreting the first item in the JSON response as a label, rather than data. By changing the code like this:
We are forcing eval to recognise the data as variable data. Now the JSON to string translation works.
