How to remember the last position read by the reader in E-book reader app?

Hi guys i developed a E-book app . It has Table of contents showing the books available to read. When you tap, the books will open and you can read it. Now i want to implement a feature when a reader close the ebook reader and opens the app he should continue reading from where he left. The app should remember the last position of the reader . I don’t know how to achieve this. Any ideas or tips are welcomed. Thanks in advance

I used this method “https://github.com/janpio/ionic-epubjs” to develop E-books . I just attached .Epub books directly to view and read it.

And i found a example here “https://github.com/pinocchio-geppetto/ionic2ebook” to remember the last position of the reader but its not in detail on he achieved it. I too used the ID and tag on my own but it didn’t work