This customization works best with Internet Explorer (Chrome has an issue with the save and close event). The script is also adapted for online instances. In case you want to change it to on-premise Dynamics 365 instances, you'll have to ensure that the Web API URL construction under checkLastModified updates accordingly and includes your organization's name.

The script is also concise and only works with Save, Save and Close, and Auto Save calls. In order to adapt it to other save methods, you'll have to add the extra save modes.

Another limitation of this customization is that it only works on updated entities--most entities in new Dynamics 365 instances (https://msdn.microsoft.com/en-us/library/gg328261.aspx#BKMK_UpdatedEntties)--as it uses the Xrm.Page.data.save() function for its callback capabilities.

Given the list of limitations and performance impact, the code in this recipe is focused more on understanding the potential Dynamics 365 client-side API capabilities as opposed to production use.