how to show date value attribute in any custom attribute of type string using script?

  I want to show the date value of type time stamp in any of the custom attribute using script based value.

i also refer the  https://jazz.net/wiki/bin/view/Main/AttributeCustomization#API_for_Javascript this Link for that. but i am getting expected results in string. this is my script code for fetching the current date

dojo.provide("org.example.workitems.providers.DateFun");
dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");
dojo.require("dojo.date");
dojo.require("dojo.date.stamp");

(function() {
var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;

dojo.declare("org.example.workitems.providers.DateFun ", null, {

    getValue: function(attributeId, workItem, configuration) {

       
      var due_date= dojo.date.stamp.fromISOString(workItem.getValue(WorkItemAttributes.DUE_DATE));
    
           return due_date;
    }
});
})();

 Please guide is this correct way to access.