how to throw server side error to javascript side[client side]

Question

I am comparing two date time fields in Apex.If start date and time is greater than end date,I have to display error in salesforceLightning component.

 Datetime EventStartDate= datetime.valueOf(stringdate1);
 Datetime EventEndDate= datetime.valueOf(stringdate2);

 if(EventStartDate< EventEndDate){    
     //How to throw this error to javascript side
 }

How to display error message in javascript side based on server side error.

Answer 1

On the server, use the AuraHandledException:

if(EventStartDate > EventEndDate) {
  throw new AuraHandledException('End date must be after start date');
}

You can then detect this situation in your controller's callback:

if(response.getState() === "ERROR") {
  // show the message with a toast or other mechanism
}

Answer 2

I think you can throw error in apex using

throw new AuraHandledException('');

More info here https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/controllers_server_apex_custom_errors.htm

Hope it will help!