After huge research, I am planning to go with JavaScript Search engine with Angular/Vue.js/Meteor/React as front-end

Choice of javascript client-side storage is below

1) IndexedDB
2) JScene
3) LargeLocalStorage
4) ydn db
5) PouchDB

Links for reference

https://github.com/tantaman/LargeLocalStorage
https://gist.github.com/inexorabletash/a279f03ab5610817c0540c83857e4295
http://lintool.github.io/JScene/
https://db-engines.com/en/system/LokiJS%3BPouchDB%3BSolr

Please kindly suggest which one to go…

Basically planning to build a cross-platform system that accepts huge files from the user and finally does a full-text search…

In this way, the user just needs the browser no installation is required……

In this way, the application will be purely portable irrespective of OS…

This would be absolutely cross-platform

Features trying to build once the files got indexed by the front-end code/logic

1) Search Box with type-ahead search
2) Combo box to choose the language
3) Number of hits should be while typing. Please type some text in and 
   you will understand what is number of hits
4) Search keyword should be highlighted in the left with portion of text.
   On clicking the text, the entire subject with highlighted search
   should shown in the right

nearly 2,000 files are in text format of 600 kB each size.

the files can be anything – log file or any text file…If support other formats also it is well and good

Please, kindly advise with suggestions or comments… As this will benefit for many…

I never come across several open source apps which does a full-text search or have the functionality which does everything in front-end or client-side

1st option which DB would be the right choice – IndexedDB or PouchDB.
2nd option would be which should be the front end.
3rd option would be how to bundle as executable exe or portable

Thanks.