This will be useful working on customised UI pages, CMS pages or content blocks. 

Depending on the jQuery version specified, some javascript functions in the out of the box files do not run properly on an CMS page. 

You can use the following command to find out if there is a different version of the jQuery library being invoked on the CMS page.

Type this command in the Chrome Developer Tools Javascript console window to see what version of the jQuery is being used on this page: 

console.log(jQuery().jquery);

Use to compare the customised page against the out of the box page.