PolyFillNotAvailable

[binli0114]

Error occurs when clicks the mail button.

(node:960) UnhandledPromiseRejectionWarning: PolyFillNotAvailable: Library cannot function without fetch. So, please provide polyfill for it.

Solution:
npm install --save isomorphic-fetch
Then
require("isomorphic-fetch"); in mail.js

[jasonjoh]

Closing this issue as I'm archiving this sample. We've retired the tutorial that this is based on and we're redirecting to the Microsoft Graph tutorial at https://docs.microsoft.com/graph/tutorials/node. The corresponding GitHub repo is https://github.com/microsoftgraph/msgraph-training-nodeexpressapp