Single sign-on using node JS HTML while already signed on on sharepoint

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SharePoint2013

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Hi All,

My requirement is like - When User is already logged into Sharepoint then he does not need to enter his/her credentials on application.
Here i am using Node JS and HTML page to fetch Sharepoint information and rendering on page.
Every time Site/application is refreshed then it's asking for user credentials.
It should not ask while user is already signed-in to Sharepoint.

What is the best way to achieve this?

What I have tried:

I have not tried anything as i have no idea and also i never worked on sharepoint.