I have created a java script for date comparison which returns error if both dates are not same, while after creating condition i did a test on the condition but on first attempt condition behave as i expect but on the second attempt condition just returns the alert  but not the ERROR.

I'm not able to figure out what's wrong with my code, if anyone could help me out to resolve this issue that would be great.

Following is my code:
dojo.provide("com.example.estimateddeploymentdatevalidation");

dojo.require("com.ibm.team.workitem.api.common.Severity");
dojo.require("com.ibm.team.workitem.api.common.Status");

(function () {

    var Severity = com.ibm.team.workitem.api.common.Severity;
    var Status = com.ibm.team.workitem.api.common.Status;

    dojo.declare("com.example.estimateddeploymentdatevalidation", null, {

        validate: function (attribute, workItem, configuration) {
  
           // require(["dojo/dom", "dojo/dom-style"], function (dom, domStyle) {

                var estimatedDate = dojo.date.stamp.fromISOString(workItem.getValue("arabbank.attribute.EstimatedDeploymentDate"));
                var deploymentDate = dojo.date.stamp.fromISOString(workItem.getValue("arabbank.attribute.DateTime"));

                if (estimatedDate != null && deploymentDate != null) {
                
                    var diff = dojo.date.difference(estimatedDate, deploymentDate, "day");
                    //alert(diff);
                    //alert(deploymentDate);
                    if (diff != 0) {
                        //alert("Inside");
                        var severity = "ERROR";
                        var message = "Estimated DeploymentDate & Deployment Date must be same";
                        alert(message);
                        return new Status(Severity[severity], message);
                    }
                }
                return Status.OK_STATUS;
            //});
          
         
        }
    });
})();