power bi api javascript 'TypeError: Cannot read properties of undefined (reading 'get')'

Hi. v-cazheng-msft

1) when i type 'npx nodemon app.js' 
    working well without any error 

2) and when i open localhost:5300 in the chrome browser 

also working.

3) but screen is changed to white without any changes few seconds later.

4) so i back to the vscode, i can see this code error.. 

5) and i don't know exactly how to embed token to my code.
if you know the way, please let me know the reference..

i followed this address : 

https://docs.microsoft.com/ko-kr/power-bi/developer/embedded/embed-sample-for-customers?tabs=net-core

i've been looking for the answer for 2 days.. it's so anoying 😞