I might be a little late to the party on this one, but I’ve just come across PreSaveAction() for SharePoint forms. This allows you to add a JavaScript function (called PreSaveAction) to a form, and it’ll get called before the form is submitted.
function PreSaveAction() { //Manipulate Fields before saving //Or perform custom validation //There's loads of uses, particularly if also using JQuery. return true; //Return false to cancel submit }
Bizarrely, this has been in SharePoint since SP2007, yet somehow I’ve not come across it before. Clearly, it isn’t as powerful as Display Templates, but that’s a nice feature!