How to fetch related records in JavaScript

Hi All,

I trying to fetch related records using the following methods,but 

  

var parentBean = app.data.createBean('parentmodule', { id: parentId });
var relatedRecords = app.data.createRelatedCollection(parentBean, 'relatedmodule');

  

relatedRecords.fetch();

But the results not displaying the related records.

Please help me to get solution for this