Find out whether potential customers reside within the service area before accepting service requests.

PROTOTYPE

template.js Client logic.

admin App Engine app that edits config, including the service area map.

sspush Cloud Function that sends usage information to the back end.

chromextension Chrome extension that writes the script tag into the target site.

Copy a credentials.json with service account credentials into the admin and sspush folders.

Place an api.json file consisting of mapsApiKey and sheetsApiKey values into the admin folder. The API keys must grant access to the Maps and Places APIs and to the Sheets API, respectively.

Place an api.json file consisting of one value, apiKey, into the sspush folder. The API key must grant access to the Sheets API.

There is as yet no provision for dev vs. prod modes. You are working with live data. Watch out.