Hi Suraj,
Can you provide your complete code for a further research?
As a common practice, I suggest you debug your code in browser using IE Developer Tools, it will give you more details about the execution of your code which would be helpful to you to find the root cause of this issue.
Debug JavaScript using IE developer tool
https://msdn.microsoft.com/en-us/library/ie/bg182326(v=vs.85)
Whats more, if you want to display the user name in a search result, please check that if there is a managed property for saving user name. If there is such managed property, you can display it by simple customizing the display template without send requests to get user names from server.
About how to display specific managed properties by customizing display template for your reference:
Thanks
Patrick Liang
Hi,
If you want to customize a item and control template for the content search web part, I suggest you refer to the OOB template.
http://blog.mmasood.com/2014/05/customising-sharepoint-2013-people.html
To display the username, please try to use the "UserName" property.
https://technet.microsoft.com/en-us/library/jj219630(v=office.15).aspx
Or please provide some code or more information for further research.
Best Regards,