Which js file load cordova-capacitor mobile app

Add the following to the bottom of the first Javascript file that loads with your app. This is <project-dir>/www/js/index.js for most Cordova projects.

I am trying to enable push notification via onesignal, i have installed the plugin, but i need to know where to add the script they provide.

I can only see routes.js file in the js folder. Is this the file that loads with the app?