While SharePoint offers a number of ways to change content structure for subsites, lists, libraries, views, columns, content types and the out-of-the-box Web parts, sometimes it’s just not enough.
There are times when users or designers and developers need to make changes to the functionality and appearance of a SharePoint site in a way that is not allowed by their IT department. Since SharePoint Designer is restricted in most organizations, it is not usually an option. Another more accessible possibility is jQuery.
JQuery is a JavaScript library that lets you manipulate the user interface of SharePoint in a way that does not impact a site beyond the page. It can do this because the code is only executed in the browser and on the Web page. It has no impact on what the server serves up, which gives users a great deal of freedom beyond the out-of-the-box functionality and UI.
Adding some jQuery code to your site is simple because SharePoint already provides the means to do it — the humble Content Editor Web Part (CEWP). While this Web part is usually used to display formatted text on a SharePoint page, it can also be used to run jQuery scripts. All you have to do is add a CEWP to your page, paste in the script, press OK or apply it. No need to compile code on the server, no complex change control procedure to get through with IT, and if it goes wrong, the worst situation is that you will have to remove the Web part from the page. The only thing you should test are browser versions, just to be sure they are compatible.
JQuery uses a library of functions hosted by Google to manipulate the data or structure (such as cascading style sheets) on your page. For that reason, most examples of jQuery you will find on the Web contain a line like this at the top:
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js" type="text/javascript"> <...
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