Friday, April 10, 2015

ScriptEditor reloads script-links

On the homepage of our SharePoint 2013 intranet we allow employees to install apps. One of them is for internal company ‘fun and facts’: Did you know? The global design of this app is a SharePoint list with the ‘fun and facts’, and jQuery script to get selected listitems via listdata.svc and bind the returned JSON data to html elements. The jQuery script is deployed to the Style Library in the site collection, and the link to this script file is provisioned to the page via a ScriptEditor webpart:
<div id="DW-DYK-Container"></div> <script type="text/javascript" src="/Style Library/Scripts/DidYouKnow.js" ></script>
For performance tuning I regularly monitor via Fiddler the http requests that the browser sends for a page visit. With the modern web applications constructed partly as html+css+javascript, the number of http requests can grow to a larger set as one is aware. In the Fiddler trace, I spotted the browser request for the script file ‘/Style Library/Scripts/DidYouKnow.js’, on which SharePoint responds with ‘304 NonModified. But to my surprise I also noticed a second Http Get request for the same script file, and this url is made unique to force renewed retrieval from the server.
I analyzed what causes this second request for the script file. My finding is that it is caused by the ScriptEditor class. The above ScriptEditor content is rendered to the following html:
SharePoint 2013 includes Embed Code handling that detects ‘orphan’ client script code in the page html, and does some magic with that. Part of that magic apparently is to force the (re)loading of script-links that are within the ‘ms-rte-embedcode’ div-element, via an equivalent of jQuery’s getScript() method (that also adds an unique part to the url to force script file reload from the server). However, from performance and in particular latency perspective, I dislike this behaviour: I do not want the extra request and certainly not the everytime renewed retrieval of the script-file of which I know it remains stable. So I came up with an approach to break out of the ‘magic’ of ScriptEditor: move the ‘script’ element outside of the ‘ms-rte-embedcode’ div-elements:
<div id="DW-DYK-Container"></div> <script language='javascript' type='text/javascript'> var head = document.getElementsByTagName('head').item(0); var script = document.createElement('script'); script.setAttribute('type', 'text/javascript'); script.setAttribute('src', '/Style Library/Scripts/DidYouKnow.js'); head.appendChild(script); </script>
I admit: the code is more complex as the initial one. But the result is what I want: no more duplicate and repetitive forced retrieval of the script file.

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