webpackJsonp is not defined


Ionic app seems to have stopped working and I am not able pinpoint the cause. I started again from blank app, but this error persists

Not sure if I am missing setup steps or issue with version mismatch? any pointers would help as I have wasted weeks on this issue

Accepted answers, like - WebpackJsonp missing after Ionic 3 update or Ionic 2: ReferenceError: webpackJsonp is not defined have not worked

index.html has

ionic info -
cli packages: (/usr/local/lib/node_modules)

@ionic/cli-utils : 1.19.2
ionic (Ionic CLI) : 3.20.0
global packages:

cordova (Cordova CLI) : 8.0.0
local packages:

@ionic/app-scripts : 3.1.8
Cordova Platforms : android 6.4.0 ios 4.5.4
Ionic Framework : ionic-angular 3.9.2

Android SDK Tools : 26.1.1
ios-deploy : 1.9.2
Node : v9.5.0
npm : 5.7.1
service.worker.js has-

// pre-cache our key assets


have you solved this issue? been losing time trying to figure out what could be wrong.