The optional/required field checks is performed when there is a submit button or some similar action taken that collects all the widget values.

Probably the best thing to do is use the createResponseObject() which can be added to an on click in a button.

https://internal.vantiq.com/docs/system/cbref/index.html#createresponseobject

You could use jQuery or something to draw some redboxes around the required fields with your own data validator like:

if(!page.data.datetime){
$(‘#divid’).css(‘border’, ‘3px solid red’);
} else {
//do the submit actions
}

You want to use page.validate() in your submit action.

For example

if(page.validate()){
console.log(page);

}

This will give prompt you like this if the optional fields are left blank. See attachment.