How to get input information on web app like msg box using google script

I need output on web app which key information in input box. using html and java script I deployed as web app. once key the information I should get pop up msg on web app that information. Please help me out of this problem.

I have created HTML and javascript, using that data is getting capture in google spreadsheet but that information I should get on web app like pop up msg

Key information get in pop up msg in web app only