TS2304 Error when building android app

I am building the Google Login from the Ionic 4 tutorial here:

When I run:
ionic cordova build android

I get the following warning:
ERROR in src/app/login/login.page.ts(31,35): error TS2304: Cannot find name ‘myWebID’.

where myWebID has been provided by google.

The catch here is when I run
ionic serve
The startup goes like:

[INFO] Development server running!

Then This error occurs:
[ng] ERROR in src/app/login/login.page.ts(31,35): error TS2304: Cannot find name ‘myWebID’.
[ng]
[ng] i 「wdm」: Failed to compile.

we see an error on localhost:8100:
Cannot GET /

I then change nothing but re-save the file login.page.ts, where my Web Client ID is stored.

Then presto it works for just ionic serve:
[ng] i 「wdm」: Compiled successfully.

Can someone please explain why my Web Client Id may not be picked up correctly initially?